diff --git a/demos/gtk-demo/blendmodes.ui b/demos/gtk-demo/blendmodes.ui
index 5826f41d44..a74ba7e4eb 100644
--- a/demos/gtk-demo/blendmodes.ui
+++ b/demos/gtk-demo/blendmodes.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow" id="window">
     <property name="resizable">0</property>
     <property name="title">CSS Blend Modes</property>
diff --git a/demos/gtk-demo/filtermodel.ui b/demos/gtk-demo/filtermodel.ui
index 2f1f00fcb1..f4f3444ee7 100644
--- a/demos/gtk-demo/filtermodel.ui
+++ b/demos/gtk-demo/filtermodel.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkListStore" id="liststore1">
     <columns>
       <column type="gint"/>
diff --git a/demos/gtk-demo/font-features.ui b/demos/gtk-demo/font-features.ui
index 1099cd08d0..8997a5ac9e 100644
--- a/demos/gtk-demo/font-features.ui
+++ b/demos/gtk-demo/font-features.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window">
     <property name="default-width">600</property>
     <property name="default-height">500</property>
diff --git a/docs/reference/gtk/migrating-3to4.md b/docs/reference/gtk/migrating-3to4.md
index e3975d8517..14591ecb86 100644
--- a/docs/reference/gtk/migrating-3to4.md
+++ b/docs/reference/gtk/migrating-3to4.md
@@ -445,6 +445,9 @@ gtk4-builder-tool simplify command can perform many of the
 necessary changes automatically, when called with the --3to4
 option. You should always review the resulting changes.
 
+The <requires> tag now supports for the 'lib' attribute the
+'gtk' value only, instead of the 'gtk+' one previously.
+
 ### Adapt to event controller API changes
 
 A few changes to the event controller and #GtkGesture APIs
diff --git a/examples/bp/gtk/help-overlay.ui b/examples/bp/gtk/help-overlay.ui
index 20be49ea24..23cfaaffd6 100644
--- a/examples/bp/gtk/help-overlay.ui
+++ b/examples/bp/gtk/help-overlay.ui
@@ -1,5 +1,4 @@
 <interface>
-  <!-- interface-requires gtk+ 3.17 -->
   <object class="GtkShortcutsWindow" id="help_overlay">
     <property name="modal">1</property>
     <child>
diff --git a/gtk/gtkbuilder.c b/gtk/gtkbuilder.c
index b6663126cf..ef1237fccc 100644
--- a/gtk/gtkbuilder.c
+++ b/gtk/gtkbuilder.c
@@ -71,7 +71,7 @@
  * element contains an `<object>` element which describes the child object.
  * The target toolkit version(s) are described by <requires> elements,
  * the “lib” attribute specifies the widget library in question (currently
- * the only supported value is “gtk+”) and the “version” attribute specifies
+ * the only supported value is “gtk”) and the “version” attribute specifies
  * the target version in the form “`<major>`.`<minor>`”. The builder will error
  * out if the version requirements are not met.
  *
diff --git a/gtk/gtkbuilderparser.c b/gtk/gtkbuilderparser.c
index 66ff6981a7..b714a8e869 100644
--- a/gtk/gtkbuilderparser.c
+++ b/gtk/gtkbuilderparser.c
@@ -2014,15 +2014,18 @@ end_element (GtkBuildableParseContext  *context,
        * required versions, possibly throw a signal allowing them
        * to check their library versions here.
        */
-      if (!strcmp (req_info->library, "gtk+"))
+      if (!strcmp (req_info->library, "gtk"))
         {
-          if (!GTK_CHECK_VERSION (req_info->major, req_info->minor, 0))
+          if (req_info->major == 4 && req_info->minor == 0)
+            {
+              /* We allow 3.99.x to pass as 4.0 */
+            }
+          else if (gtk_check_version (req_info->major, req_info->minor, 0) != NULL)
             {
               g_set_error (error,
                            GTK_BUILDER_ERROR,
                            GTK_BUILDER_ERROR_VERSION_MISMATCH,
-                           "Required %s version %d.%d, current version is %d.%d",
-                           req_info->library,
+                           "Required GTK version %d.%d, current version is %d.%d",
                            req_info->major, req_info->minor,
                            GTK_MAJOR_VERSION, GTK_MINOR_VERSION);
               _gtk_builder_prefix_error (data->builder, context, error);
diff --git a/gtk/tools/gtk-builder-tool-simplify.c b/gtk/tools/gtk-builder-tool-simplify.c
index d40556b0cb..868d0dc49a 100644
--- a/gtk/tools/gtk-builder-tool-simplify.c
+++ b/gtk/tools/gtk-builder-tool-simplify.c
@@ -62,6 +62,7 @@ typedef struct {
   char *output_filename;
   FILE *output;
   gboolean convert3to4;
+  gboolean has_gtk_requires;
 } MyParserData;
 
 static void
@@ -1635,6 +1636,17 @@ rewrite_scale (Element      *element,
     }
 }
 
+static void
+rewrite_requires (Element      *element,
+                  MyParserData *data)
+{
+  if (has_attribute (element, "lib", "gtk+"))
+    {
+      set_attribute_value (element, "lib", "gtk");
+      set_attribute_value (element, "version", "4.0");
+    }
+}
+
 static void
 rewrite_overlay (Element      *element,
                  MyParserData *data)
@@ -1978,6 +1990,9 @@ rewrite_element (Element      *element,
       property_has_been_removed (element, data))
     return TRUE;
 
+  if (g_str_equal (element->element_name, "requires"))
+    rewrite_requires (element, data);
+
   return FALSE;
 }
 
@@ -2039,6 +2054,12 @@ enhance_element (Element      *element,
 {
   GList *l;
 
+  if (strcmp (element->element_name, "requires") == 0 &&
+      has_attribute (element, "lib", "gtk+"))
+    {
+      data->has_gtk_requires = TRUE;
+    }
+
   add_old_default_properties (element, data);
 
   for (l = element->children; l; l = l->next)
@@ -2046,6 +2067,13 @@ enhance_element (Element      *element,
       Element *child = l->data;
       enhance_element (child, data);
     }
+
+  if (element == data->root && !data->has_gtk_requires)
+    {
+      Element *requires = add_element (element, "requires");
+      set_attribute_value (requires, "lib", "gtk+");
+      set_attribute_value (requires, "version", "3.0");
+    }
 }
 
 static void
@@ -2133,6 +2161,7 @@ simplify_file (const char *filename,
   data.input_filename = filename;
   data.output_filename = NULL;
   data.convert3to4 = convert3to4;
+  data.has_gtk_requires = FALSE;
 
   if (replace)
     {
diff --git a/gtk/ui/gtkplacesview.ui b/gtk/ui/gtkplacesview.ui
index 98460819b1..7c5a927ae2 100644
--- a/gtk/ui/gtkplacesview.ui
+++ b/gtk/ui/gtkplacesview.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface domain="gtk40">
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkListStore" id="completion_store">
     <columns>
       <column type="gchararray"/>
diff --git a/gtk/ui/gtkplacesviewrow.ui b/gtk/ui/gtkplacesviewrow.ui
index 915d20a189..1941c222a3 100644
--- a/gtk/ui/gtkplacesviewrow.ui
+++ b/gtk/ui/gtkplacesviewrow.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface domain="gtk40">
-  <requires lib="gtk+" version="3.16"/>
   <template class="GtkPlacesViewRow" parent="GtkListBoxRow">
     <property name="width-request">100</property>
     <property name="child">
diff --git a/tests/testheightforwidth.c b/tests/testheightforwidth.c
index 6f78af2d47..a6b79357fc 100644
--- a/tests/testheightforwidth.c
+++ b/tests/testheightforwidth.c
@@ -37,7 +37,7 @@ static TestInterface interfaces[] = {
     "Ellipsizing Labels",
     "Demonstrates how labels will request a natural size in a horizontal space",
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">450</property>"
@@ -86,7 +86,7 @@ static TestInterface interfaces[] = {
     "Wrapping Label",
     "Demonstrates how a wrapping label can require a height contextual to its allocated width",
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">300</property>"
@@ -162,7 +162,7 @@ static TestInterface interfaces[] = {
     "Horizontal Box",
     "Demonstrates how a horizontal box can calculate the collective height for an allocated width",
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_height\">200</property>"
@@ -240,7 +240,7 @@ static TestInterface interfaces[] = {
     "This test demonstrates how \"width-chars\" and \"max-width-chars\" can be used "
     "to effect minimum and natural widths in wrapping labels.",
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">900</property>"
@@ -334,7 +334,7 @@ static TestInterface interfaces[] = {
     "and also trade height for width.",
     "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">500</property>"
@@ -394,7 +394,7 @@ static TestInterface interfaces[] = {
     "and also trade height for width.",
     "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">400</property>"
@@ -427,7 +427,7 @@ static TestInterface interfaces[] = {
     "This test shows wrapping and ellipsizing text in combo boxes (and consequently in menu items).",
     "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"3.22\"/>"
+    "  <requires lib=\"gtk\" version=\"3.99\"/>"
     "  <!-- interface-naming-policy project-wide -->"
     "  <object class=\"GtkWindow\" id=\"window\">"
     "    <property name=\"default_width\">600</property>"
diff --git a/testsuite/css/change/test1.ui b/testsuite/css/change/test1.ui
index 0ce6a0c22e..42092dec37 100644
--- a/testsuite/css/change/test1.ui
+++ b/testsuite/css/change/test1.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/change/test2.ui b/testsuite/css/change/test2.ui
index be2230727f..dfa46b711f 100644
--- a/testsuite/css/change/test2.ui
+++ b/testsuite/css/change/test2.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/css/change/test3.ui b/testsuite/css/change/test3.ui
index 0ce6a0c22e..42092dec37 100644
--- a/testsuite/css/change/test3.ui
+++ b/testsuite/css/change/test3.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/change/test4.ui b/testsuite/css/change/test4.ui
index bb70d8f4e0..652c017bae 100644
--- a/testsuite/css/change/test4.ui
+++ b/testsuite/css/change/test4.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/nodes/scale.ui b/testsuite/css/nodes/scale.ui
index 1c7eb2c251..9bfbd8f510 100644
--- a/testsuite/css/nodes/scale.ui
+++ b/testsuite/css/nodes/scale.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkAdjustment" id="adjustment1">
     <property name="lower">0</property>
     <property name="upper">100</property>
diff --git a/testsuite/css/style/adjacent-states.ui b/testsuite/css/style/adjacent-states.ui
index 61b58105b0..58266374d7 100644
--- a/testsuite/css/style/adjacent-states.ui
+++ b/testsuite/css/style/adjacent-states.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/colornames.ui b/testsuite/css/style/colornames.ui
index b9be94e3ac..7eca215155 100644
--- a/testsuite/css/style/colornames.ui
+++ b/testsuite/css/style/colornames.ui
@@ -1,7 +1,6 @@
 
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/currentcolor.ui b/testsuite/css/style/currentcolor.ui
index 7a00781bc9..50aca9e92f 100644
--- a/testsuite/css/style/currentcolor.ui
+++ b/testsuite/css/style/currentcolor.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/font.ui b/testsuite/css/style/font.ui
index 0a45a10835..2dd3f6f7b2 100644
--- a/testsuite/css/style/font.ui
+++ b/testsuite/css/style/font.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/gradient.ui b/testsuite/css/style/gradient.ui
index 6c4715f6f5..db658346c0 100644
--- a/testsuite/css/style/gradient.ui
+++ b/testsuite/css/style/gradient.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/inherit.ui b/testsuite/css/style/inherit.ui
index 8b675ea598..4eda541b15 100644
--- a/testsuite/css/style/inherit.ui
+++ b/testsuite/css/style/inherit.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/label.ui b/testsuite/css/style/label.ui
index 7a00781bc9..50aca9e92f 100644
--- a/testsuite/css/style/label.ui
+++ b/testsuite/css/style/label.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/css/style/nth-child.ui b/testsuite/css/style/nth-child.ui
index 267d4abba4..e50600f096 100644
--- a/testsuite/css/style/nth-child.ui
+++ b/testsuite/css/style/nth-child.ui
@@ -1,7 +1,5 @@
-
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="can_focus">False</property>
     <property name="decorated">0</property>
diff --git a/testsuite/gtk/builder.c b/testsuite/gtk/builder.c
index d57b676d56..88e25e7229 100644
--- a/testsuite/gtk/builder.c
+++ b/testsuite/gtk/builder.c
@@ -1829,7 +1829,7 @@ test_requires (void)
   char       *buffer;
   const char buffer_fmt[] =
     "<interface>"
-    "  <requires lib=\"gtk+\" version=\"%d.%d\"/>"
+    "  <requires lib=\"gtk\" version=\"%d.%d\"/>"
     "</interface>";
 
   buffer = g_strdup_printf (buffer_fmt, GTK_MAJOR_VERSION, GTK_MINOR_VERSION + 1);
@@ -2307,9 +2307,8 @@ test_anaconda_signal (void)
   GtkBuilder *builder;
   const char buffer[] = 
     "<?xml version='1.0' encoding='UTF-8'?>"
-    "<!-- Generated with glade 3.18.3 -->"
     "<interface>"
-    "  <requires lib='gtk+' version='3.12'/>"
+    "  <requires lib='gtk' version='3.99'/>"
     "  <object class='GtkListStore' id='liststore1'>"
     "    <columns>"
     "      <!-- column-name use -->"
diff --git a/testsuite/reftests/animation-direction.ref.ui b/testsuite/reftests/animation-direction.ref.ui
index 5c2f97aaef..75d34a43c1 100644
--- a/testsuite/reftests/animation-direction.ref.ui
+++ b/testsuite/reftests/animation-direction.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/animation-direction.ui b/testsuite/reftests/animation-direction.ui
index bf4e6cb43e..70fb039efb 100644
--- a/testsuite/reftests/animation-direction.ui
+++ b/testsuite/reftests/animation-direction.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/animation-fill-mode-iteration-count.ref.ui b/testsuite/reftests/animation-fill-mode-iteration-count.ref.ui
index 1287c040c3..6ce777e8ec 100644
--- a/testsuite/reftests/animation-fill-mode-iteration-count.ref.ui
+++ b/testsuite/reftests/animation-fill-mode-iteration-count.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/reftests/animation-fill-mode-iteration-count.ui b/testsuite/reftests/animation-fill-mode-iteration-count.ui
index 4b58c08af1..45d463a09a 100644
--- a/testsuite/reftests/animation-fill-mode-iteration-count.ui
+++ b/testsuite/reftests/animation-fill-mode-iteration-count.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/reftests/border-corner-zero-width-rendering.ref.ui b/testsuite/reftests/border-corner-zero-width-rendering.ref.ui
index 2b111b6855..ca0ca5313b 100644
--- a/testsuite/reftests/border-corner-zero-width-rendering.ref.ui
+++ b/testsuite/reftests/border-corner-zero-width-rendering.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/border-corner-zero-width-rendering.ui b/testsuite/reftests/border-corner-zero-width-rendering.ui
index 21c1f7e72d..fbaefe8b18 100644
--- a/testsuite/reftests/border-corner-zero-width-rendering.ui
+++ b/testsuite/reftests/border-corner-zero-width-rendering.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/box-order.ref.ui b/testsuite/reftests/box-order.ref.ui
index 5cf8975e94..192e27a8e7 100644
--- a/testsuite/reftests/box-order.ref.ui
+++ b/testsuite/reftests/box-order.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/box-order.ui b/testsuite/reftests/box-order.ui
index 1e1f18b07b..06689143e0 100644
--- a/testsuite/reftests/box-order.ui
+++ b/testsuite/reftests/box-order.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/box-shadow-changes-modify-clip.ref.ui b/testsuite/reftests/box-shadow-changes-modify-clip.ref.ui
index fbcf495923..885541bcc7 100644
--- a/testsuite/reftests/box-shadow-changes-modify-clip.ref.ui
+++ b/testsuite/reftests/box-shadow-changes-modify-clip.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/box-shadow-changes-modify-clip.ui b/testsuite/reftests/box-shadow-changes-modify-clip.ui
index 0913545288..9721f681f2 100644
--- a/testsuite/reftests/box-shadow-changes-modify-clip.ui
+++ b/testsuite/reftests/box-shadow-changes-modify-clip.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/box-shadow-spread.ref.ui b/testsuite/reftests/box-shadow-spread.ref.ui
index 0303ab9ebb..a5eb2bf719 100644
--- a/testsuite/reftests/box-shadow-spread.ref.ui
+++ b/testsuite/reftests/box-shadow-spread.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/box-shadow-spread.ui b/testsuite/reftests/box-shadow-spread.ui
index 216df0d516..3024ee0996 100644
--- a/testsuite/reftests/box-shadow-spread.ui
+++ b/testsuite/reftests/box-shadow-spread.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/box-shadow-with-blend-mode.ref.ui b/testsuite/reftests/box-shadow-with-blend-mode.ref.ui
index a553811ca6..bd9dc0842f 100644
--- a/testsuite/reftests/box-shadow-with-blend-mode.ref.ui
+++ b/testsuite/reftests/box-shadow-with-blend-mode.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/box-shadow-with-blend-mode.ui b/testsuite/reftests/box-shadow-with-blend-mode.ui
index b53fad608e..4f1e19de89 100644
--- a/testsuite/reftests/box-shadow-with-blend-mode.ui
+++ b/testsuite/reftests/box-shadow-with-blend-mode.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/css-em-label-size.ref.ui b/testsuite/reftests/css-em-label-size.ref.ui
index 85f4f83069..6e13c192d0 100644
--- a/testsuite/reftests/css-em-label-size.ref.ui
+++ b/testsuite/reftests/css-em-label-size.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/css-em-label-size.ui b/testsuite/reftests/css-em-label-size.ui
index fa89508222..029ab5c255 100644
--- a/testsuite/reftests/css-em-label-size.ui
+++ b/testsuite/reftests/css-em-label-size.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/css-rem-label-size.ref.ui b/testsuite/reftests/css-rem-label-size.ref.ui
index 85fe92601c..05411b7e55 100644
--- a/testsuite/reftests/css-rem-label-size.ref.ui
+++ b/testsuite/reftests/css-rem-label-size.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/css-rem-label-size.ui b/testsuite/reftests/css-rem-label-size.ui
index b3579624e8..75a07fd12d 100644
--- a/testsuite/reftests/css-rem-label-size.ui
+++ b/testsuite/reftests/css-rem-label-size.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/flipping-icons.ref.ui b/testsuite/reftests/flipping-icons.ref.ui
index 4116f12838..184aba4424 100644
--- a/testsuite/reftests/flipping-icons.ref.ui
+++ b/testsuite/reftests/flipping-icons.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/flipping-icons.ui b/testsuite/reftests/flipping-icons.ui
index 688c1495bd..830eca63df 100644
--- a/testsuite/reftests/flipping-icons.ui
+++ b/testsuite/reftests/flipping-icons.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <signal name="map" handler="reftest:switch_default_direction" swapped="no"/>
diff --git a/testsuite/reftests/gtk-icontheme-sizing.ref.ui b/testsuite/reftests/gtk-icontheme-sizing.ref.ui
index 800b02e63d..f4a12a49df 100644
--- a/testsuite/reftests/gtk-icontheme-sizing.ref.ui
+++ b/testsuite/reftests/gtk-icontheme-sizing.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/gtk-icontheme-sizing.ui b/testsuite/reftests/gtk-icontheme-sizing.ui
index 714c9cee82..031152b626 100644
--- a/testsuite/reftests/gtk-icontheme-sizing.ui
+++ b/testsuite/reftests/gtk-icontheme-sizing.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/icon-effect-missing.ref.ui b/testsuite/reftests/icon-effect-missing.ref.ui
index ee9b2657c7..827aaa9dcb 100644
--- a/testsuite/reftests/icon-effect-missing.ref.ui
+++ b/testsuite/reftests/icon-effect-missing.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/icon-effect-missing.ui b/testsuite/reftests/icon-effect-missing.ui
index 7d77f96e2f..cee553e94c 100644
--- a/testsuite/reftests/icon-effect-missing.ui
+++ b/testsuite/reftests/icon-effect-missing.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.16"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/icon-shadow-no-transform.ref.ui b/testsuite/reftests/icon-shadow-no-transform.ref.ui
index 51ecb0a95d..5082088037 100644
--- a/testsuite/reftests/icon-shadow-no-transform.ref.ui
+++ b/testsuite/reftests/icon-shadow-no-transform.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/icon-shadow-no-transform.ui b/testsuite/reftests/icon-shadow-no-transform.ui
index 3c4b93831f..2e6acadce2 100644
--- a/testsuite/reftests/icon-shadow-no-transform.ui
+++ b/testsuite/reftests/icon-shadow-no-transform.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/icon-style-basics.ref.ui b/testsuite/reftests/icon-style-basics.ref.ui
index 55301e93e4..e48c110705 100644
--- a/testsuite/reftests/icon-style-basics.ref.ui
+++ b/testsuite/reftests/icon-style-basics.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkListStore" id="liststore1">
     <columns>
       <column type="gchararray"/>
diff --git a/testsuite/reftests/icon-style-basics.ui b/testsuite/reftests/icon-style-basics.ui
index 0b79f497c9..8614571ec7 100644
--- a/testsuite/reftests/icon-style-basics.ui
+++ b/testsuite/reftests/icon-style-basics.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkListStore" id="liststore1">
     <columns>
       <column type="gchararray"/>
diff --git a/testsuite/reftests/icon-vfuncs.ref.ui b/testsuite/reftests/icon-vfuncs.ref.ui
index 4d625e9945..9d9d8b1b77 100644
--- a/testsuite/reftests/icon-vfuncs.ref.ui
+++ b/testsuite/reftests/icon-vfuncs.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/reftests/icon-vfuncs.ui b/testsuite/reftests/icon-vfuncs.ui
index 1d7bd31bbe..a2e619ba4f 100644
--- a/testsuite/reftests/icon-vfuncs.ui
+++ b/testsuite/reftests/icon-vfuncs.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/reftests/image-icon-name-use-fallback.ref.ui b/testsuite/reftests/image-icon-name-use-fallback.ref.ui
index 49815a302a..e9ab9b2f3a 100644
--- a/testsuite/reftests/image-icon-name-use-fallback.ref.ui
+++ b/testsuite/reftests/image-icon-name-use-fallback.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.10"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/image-icon-name-use-fallback.ui b/testsuite/reftests/image-icon-name-use-fallback.ui
index b353ed4721..669c89d348 100644
--- a/testsuite/reftests/image-icon-name-use-fallback.ui
+++ b/testsuite/reftests/image-icon-name-use-fallback.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.10"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/image-icon-shadow-clipping.ref.ui b/testsuite/reftests/image-icon-shadow-clipping.ref.ui
index 36813408f9..b1d8ee93ac 100644
--- a/testsuite/reftests/image-icon-shadow-clipping.ref.ui
+++ b/testsuite/reftests/image-icon-shadow-clipping.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/image-icon-shadow-clipping.ui b/testsuite/reftests/image-icon-shadow-clipping.ui
index fa151544fa..5a04725bb9 100644
--- a/testsuite/reftests/image-icon-shadow-clipping.ui
+++ b/testsuite/reftests/image-icon-shadow-clipping.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-background.ref.ui b/testsuite/reftests/label-background.ref.ui
index e6a46ecbb8..d78bbab469 100644
--- a/testsuite/reftests/label-background.ref.ui
+++ b/testsuite/reftests/label-background.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/label-background.ui b/testsuite/reftests/label-background.ui
index e2665bd2eb..9384d15fb8 100644
--- a/testsuite/reftests/label-background.ui
+++ b/testsuite/reftests/label-background.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/label-box-shadow-clip.ref.ui b/testsuite/reftests/label-box-shadow-clip.ref.ui
index b6b0b04041..f8d67fcf16 100644
--- a/testsuite/reftests/label-box-shadow-clip.ref.ui
+++ b/testsuite/reftests/label-box-shadow-clip.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-box-shadow-clip.ui b/testsuite/reftests/label-box-shadow-clip.ui
index 0047f8c25e..918a24f9ed 100644
--- a/testsuite/reftests/label-box-shadow-clip.ui
+++ b/testsuite/reftests/label-box-shadow-clip.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-clipping.ref.ui b/testsuite/reftests/label-clipping.ref.ui
index 83db896757..1713383794 100644
--- a/testsuite/reftests/label-clipping.ref.ui
+++ b/testsuite/reftests/label-clipping.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="decorated">0</property>
diff --git a/testsuite/reftests/label-clipping.ui b/testsuite/reftests/label-clipping.ui
index 45c6ca8138..2aa314b227 100644
--- a/testsuite/reftests/label-clipping.ui
+++ b/testsuite/reftests/label-clipping.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="decorated">0</property>
diff --git a/testsuite/reftests/label-text-shadow-changes-modify-clip.ref.ui b/testsuite/reftests/label-text-shadow-changes-modify-clip.ref.ui
index 73b8efb450..92f9850e84 100644
--- a/testsuite/reftests/label-text-shadow-changes-modify-clip.ref.ui
+++ b/testsuite/reftests/label-text-shadow-changes-modify-clip.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-text-shadow-changes-modify-clip.ui b/testsuite/reftests/label-text-shadow-changes-modify-clip.ui
index 0913545288..9721f681f2 100644
--- a/testsuite/reftests/label-text-shadow-changes-modify-clip.ui
+++ b/testsuite/reftests/label-text-shadow-changes-modify-clip.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-text-shadow-clipping.ref.ui b/testsuite/reftests/label-text-shadow-clipping.ref.ui
index 2d15374f73..0e25bcf84c 100644
--- a/testsuite/reftests/label-text-shadow-clipping.ref.ui
+++ b/testsuite/reftests/label-text-shadow-clipping.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/label-text-shadow-clipping.ui b/testsuite/reftests/label-text-shadow-clipping.ui
index 5b581f8277..04d5eff61c 100644
--- a/testsuite/reftests/label-text-shadow-clipping.ui
+++ b/testsuite/reftests/label-text-shadow-clipping.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">500</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/letter-spacing.ref.ui b/testsuite/reftests/letter-spacing.ref.ui
index dbd264b6ed..0ad6e4c1c1 100644
--- a/testsuite/reftests/letter-spacing.ref.ui
+++ b/testsuite/reftests/letter-spacing.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/notebook-tab-position.ref.ui b/testsuite/reftests/notebook-tab-position.ref.ui
index b8b636f935..a7ce7d4fc5 100644
--- a/testsuite/reftests/notebook-tab-position.ref.ui
+++ b/testsuite/reftests/notebook-tab-position.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/notebook-tab-position.ui b/testsuite/reftests/notebook-tab-position.ui
index c164a20961..4dc7df16c0 100644
--- a/testsuite/reftests/notebook-tab-position.ui
+++ b/testsuite/reftests/notebook-tab-position.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/opacity-initial.ref.ui b/testsuite/reftests/opacity-initial.ref.ui
index 32b8fc9bb5..9c18708dff 100644
--- a/testsuite/reftests/opacity-initial.ref.ui
+++ b/testsuite/reftests/opacity-initial.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">200</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/opacity-initial.ui b/testsuite/reftests/opacity-initial.ui
index e3116565b2..da36f52e70 100644
--- a/testsuite/reftests/opacity-initial.ui
+++ b/testsuite/reftests/opacity-initial.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">200</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/overlay-no-main-widget.ref.ui b/testsuite/reftests/overlay-no-main-widget.ref.ui
index 8327429142..df4f73e661 100644
--- a/testsuite/reftests/overlay-no-main-widget.ref.ui
+++ b/testsuite/reftests/overlay-no-main-widget.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkOverlay" id="overlay1">
diff --git a/testsuite/reftests/overlay-no-main-widget.ui b/testsuite/reftests/overlay-no-main-widget.ui
index eaca0f2d0f..d5f262efa1 100644
--- a/testsuite/reftests/overlay-no-main-widget.ui
+++ b/testsuite/reftests/overlay-no-main-widget.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkOverlay" id="overlay1">
diff --git a/testsuite/reftests/pseudoclass-on-box.ref.ui b/testsuite/reftests/pseudoclass-on-box.ref.ui
index 375e83f54c..e528e91702 100644
--- a/testsuite/reftests/pseudoclass-on-box.ref.ui
+++ b/testsuite/reftests/pseudoclass-on-box.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/pseudoclass-on-box.ui b/testsuite/reftests/pseudoclass-on-box.ui
index e16fdf911e..b9cc7f604d 100644
--- a/testsuite/reftests/pseudoclass-on-box.ui
+++ b/testsuite/reftests/pseudoclass-on-box.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/pseudoclass-on-parent.ref.ui b/testsuite/reftests/pseudoclass-on-parent.ref.ui
index c9933fda8e..42275aa763 100644
--- a/testsuite/reftests/pseudoclass-on-parent.ref.ui
+++ b/testsuite/reftests/pseudoclass-on-parent.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/pseudoclass-on-parent.ui b/testsuite/reftests/pseudoclass-on-parent.ui
index beccde56d0..250a97da40 100644
--- a/testsuite/reftests/pseudoclass-on-parent.ui
+++ b/testsuite/reftests/pseudoclass-on-parent.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/set-default-direction.ref.ui b/testsuite/reftests/set-default-direction.ref.ui
index d54ff23ba8..8538127aae 100644
--- a/testsuite/reftests/set-default-direction.ref.ui
+++ b/testsuite/reftests/set-default-direction.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <signal name="realize" handler="reftest:switch_default_direction" after="yes" swapped="no"/>
diff --git a/testsuite/reftests/set-default-direction.ui b/testsuite/reftests/set-default-direction.ui
index 80a013e57d..3c3fb75843 100644
--- a/testsuite/reftests/set-default-direction.ui
+++ b/testsuite/reftests/set-default-direction.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <signal name="map" handler="reftest:switch_default_direction" swapped="no"/>
diff --git a/testsuite/reftests/shadow-clip-rounding.ref.ui b/testsuite/reftests/shadow-clip-rounding.ref.ui
index b6b0b04041..f8d67fcf16 100644
--- a/testsuite/reftests/shadow-clip-rounding.ref.ui
+++ b/testsuite/reftests/shadow-clip-rounding.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/shadow-clip-rounding.ui b/testsuite/reftests/shadow-clip-rounding.ui
index 0047f8c25e..918a24f9ed 100644
--- a/testsuite/reftests/shadow-clip-rounding.ui
+++ b/testsuite/reftests/shadow-clip-rounding.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">100</property>
     <property name="height_request">100</property>
diff --git a/testsuite/reftests/sibling-pseudoclasses.ref.ui b/testsuite/reftests/sibling-pseudoclasses.ref.ui
index 0ec480703a..72fb91086a 100644
--- a/testsuite/reftests/sibling-pseudoclasses.ref.ui
+++ b/testsuite/reftests/sibling-pseudoclasses.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkBox" id="box1">
diff --git a/testsuite/reftests/sibling-pseudoclasses.ui b/testsuite/reftests/sibling-pseudoclasses.ui
index f22e0cc63f..fa3f79720f 100644
--- a/testsuite/reftests/sibling-pseudoclasses.ui
+++ b/testsuite/reftests/sibling-pseudoclasses.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkBox" id="box1">
diff --git a/testsuite/reftests/statusbar-remove-all.ref.ui b/testsuite/reftests/statusbar-remove-all.ref.ui
index 6bda5b3922..18bce2eda3 100644
--- a/testsuite/reftests/statusbar-remove-all.ref.ui
+++ b/testsuite/reftests/statusbar-remove-all.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/statusbar-remove-all.ui b/testsuite/reftests/statusbar-remove-all.ui
index 0baf34621e..bfe4821efb 100644
--- a/testsuite/reftests/statusbar-remove-all.ui
+++ b/testsuite/reftests/statusbar-remove-all.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/style-context-save-inheritance.ref.ui b/testsuite/reftests/style-context-save-inheritance.ref.ui
index d3745e4bd7..144e4ed259 100644
--- a/testsuite/reftests/style-context-save-inheritance.ref.ui
+++ b/testsuite/reftests/style-context-save-inheritance.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/style-context-save-inheritance.ui b/testsuite/reftests/style-context-save-inheritance.ui
index c058490869..e489ed80c4 100644
--- a/testsuite/reftests/style-context-save-inheritance.ui
+++ b/testsuite/reftests/style-context-save-inheritance.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/textview-border-windows.ref.ui b/testsuite/reftests/textview-border-windows.ref.ui
index 1bb083dad4..45f770a132 100644
--- a/testsuite/reftests/textview-border-windows.ref.ui
+++ b/testsuite/reftests/textview-border-windows.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkWindow" id="window">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/textview-border-windows.ui b/testsuite/reftests/textview-border-windows.ui
index dc51f0091e..1c3cb81829 100644
--- a/testsuite/reftests/textview-border-windows.ui
+++ b/testsuite/reftests/textview-border-windows.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkWindow" id="window">
     <property name="decorated">0</property>
     <child>
diff --git a/testsuite/reftests/textview-margins.ref.ui b/testsuite/reftests/textview-margins.ref.ui
index 190201d3a5..510afd9fad 100644
--- a/testsuite/reftests/textview-margins.ref.ui
+++ b/testsuite/reftests/textview-margins.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkTextBuffer" id="textbuffer1">
     <property name="text" translatable="yes">Lorem ipsum dolor sit amet, consectetur adipisci elit, sed eiusmod tempor incidunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquid ex ea commodi consequat. Quis aute iure reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint obcaecat cupiditat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum</property>
   </object>
diff --git a/testsuite/reftests/textview-margins.ui b/testsuite/reftests/textview-margins.ui
index 93dd2ab9c2..340c849138 100644
--- a/testsuite/reftests/textview-margins.ui
+++ b/testsuite/reftests/textview-margins.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkTextBuffer" id="textbuffer1">
     <property name="text" translatable="yes">Lorem ipsum dolor sit amet, consectetur adipisci elit, sed eiusmod tempor incidunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquid ex ea commodi consequat. Quis aute iure reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint obcaecat cupiditat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum</property>
   </object>
diff --git a/testsuite/reftests/treeview-crash-too-wide.ref.ui b/testsuite/reftests/treeview-crash-too-wide.ref.ui
index ad9eb85c61..fc2094c48e 100644
--- a/testsuite/reftests/treeview-crash-too-wide.ref.ui
+++ b/testsuite/reftests/treeview-crash-too-wide.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkListStore" id="liststore1">
     <columns>
       <column type="gchararray"/>
diff --git a/testsuite/reftests/treeview-crash-too-wide.ui b/testsuite/reftests/treeview-crash-too-wide.ui
index ad9eb85c61..fc2094c48e 100644
--- a/testsuite/reftests/treeview-crash-too-wide.ui
+++ b/testsuite/reftests/treeview-crash-too-wide.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkListStore" id="liststore1">
     <columns>
       <column type="gchararray"/>
diff --git a/testsuite/reftests/window-show-contents-on-map.ref.ui b/testsuite/reftests/window-show-contents-on-map.ref.ui
index d074202b08..f24540ed6b 100644
--- a/testsuite/reftests/window-show-contents-on-map.ref.ui
+++ b/testsuite/reftests/window-show-contents-on-map.ref.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="width_request">200</property>
     <property name="height_request">200</property>
diff --git a/testsuite/reftests/window-show-contents-on-map.ui b/testsuite/reftests/window-show-contents-on-map.ui
index ec617ace22..88e00d8e51 100644
--- a/testsuite/reftests/window-show-contents-on-map.ui
+++ b/testsuite/reftests/window-show-contents-on-map.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.12"/>
   <object class="GtkWindow" id="window1">
     <property name="decorated">0</property>
     <signal name="map" handler="gtk_widget_show" object="label1" after="yes" swapped="yes"/>
diff --git a/testsuite/tools/simplify-data-3to4/actionbar.expected b/testsuite/tools/simplify-data-3to4/actionbar.expected
index a063c7f2b6..f356da78aa 100644
--- a/testsuite/tools/simplify-data-3to4/actionbar.expected
+++ b/testsuite/tools/simplify-data-3to4/actionbar.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkActionBar">
     <property name="visible">0</property>
     <child type="start">
diff --git a/testsuite/tools/simplify-data-3to4/actionbar.ui b/testsuite/tools/simplify-data-3to4/actionbar.ui
index efae5962d9..7128aa8945 100644
--- a/testsuite/tools/simplify-data-3to4/actionbar.ui
+++ b/testsuite/tools/simplify-data-3to4/actionbar.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkActionBar">
     <child>
       <object class="GtkButton" id="button">
diff --git a/testsuite/tools/simplify-data-3to4/assistant.expected b/testsuite/tools/simplify-data-3to4/assistant.expected
index 906c68c4b2..532abbb701 100644
--- a/testsuite/tools/simplify-data-3to4/assistant.expected
+++ b/testsuite/tools/simplify-data-3to4/assistant.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkAssistant" id="window1">
     <child>
       <object class="GtkAssistantPage">
diff --git a/testsuite/tools/simplify-data-3to4/assistant.ui b/testsuite/tools/simplify-data-3to4/assistant.ui
index e731f51245..83d1dfe908 100644
--- a/testsuite/tools/simplify-data-3to4/assistant.ui
+++ b/testsuite/tools/simplify-data-3to4/assistant.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkAssistant" id="window1">
     <child>
       <object class="GtkButton" id="button1">
diff --git a/testsuite/tools/simplify-data-3to4/bin.expected b/testsuite/tools/simplify-data-3to4/bin.expected
index 52b3f1c633..f6af9712b6 100644
--- a/testsuite/tools/simplify-data-3to4/bin.expected
+++ b/testsuite/tools/simplify-data-3to4/bin.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkFrame">
     <property name="visible">0</property>
     <property name="label">bla</property>
diff --git a/testsuite/tools/simplify-data-3to4/box.expected b/testsuite/tools/simplify-data-3to4/box.expected
index 9f62a3b09e..3d452aca8b 100644
--- a/testsuite/tools/simplify-data-3to4/box.expected
+++ b/testsuite/tools/simplify-data-3to4/box.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow">
     <property name="child">
       <object class="GtkBox">
diff --git a/testsuite/tools/simplify-data-3to4/box.ui b/testsuite/tools/simplify-data-3to4/box.ui
index fad61969e8..ece4ca7eee 100644
--- a/testsuite/tools/simplify-data-3to4/box.ui
+++ b/testsuite/tools/simplify-data-3to4/box.ui
@@ -1,7 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.22.2 -->
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkWindow">
     <child>
       <object class="GtkBox">
diff --git a/testsuite/tools/simplify-data-3to4/dialog.expected b/testsuite/tools/simplify-data-3to4/dialog.expected
index 5742f71e02..24c975fd76 100644
--- a/testsuite/tools/simplify-data-3to4/dialog.expected
+++ b/testsuite/tools/simplify-data-3to4/dialog.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <object class="GtkDialog">
+  <requires lib="gtk" version="4.0"/>
   <child internal-child="content_area">
     <object class="GtkBox">
       <property name="visible">0</property>
diff --git a/testsuite/tools/simplify-data-3to4/fixed.expected b/testsuite/tools/simplify-data-3to4/fixed.expected
index 74953b12c6..2ba12071ed 100644
--- a/testsuite/tools/simplify-data-3to4/fixed.expected
+++ b/testsuite/tools/simplify-data-3to4/fixed.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkFixed">
     <child>
       <object class="GtkButton" id="button">
diff --git a/testsuite/tools/simplify-data-3to4/fixed.ui b/testsuite/tools/simplify-data-3to4/fixed.ui
index 699bea2e07..8eca6d0125 100644
--- a/testsuite/tools/simplify-data-3to4/fixed.ui
+++ b/testsuite/tools/simplify-data-3to4/fixed.ui
@@ -1,7 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.22.2 -->
 <interface>
-  <requires lib="gtk+" version="3.0"/>
   <object class="GtkFixed">
     <property name="visible">True</property>
     <child>
diff --git a/testsuite/tools/simplify-data-3to4/grid.expected b/testsuite/tools/simplify-data-3to4/grid.expected
index 517dcd0f1d..b2f4f733aa 100644
--- a/testsuite/tools/simplify-data-3to4/grid.expected
+++ b/testsuite/tools/simplify-data-3to4/grid.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="window1">
     <property name="child">
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/tools/simplify-data-3to4/grid.ui b/testsuite/tools/simplify-data-3to4/grid.ui
index a853331dc5..110baf2d64 100644
--- a/testsuite/tools/simplify-data-3to4/grid.ui
+++ b/testsuite/tools/simplify-data-3to4/grid.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkGrid" id="grid1">
diff --git a/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.expected b/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.expected
index 11a691763d..b96ec784d8 100644
--- a/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.expected
+++ b/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface domain="gtk30">
+  <requires lib="gtk" version="4.0"/>
   <template class="GtkFileChooserDialog" parent="GtkDialog">
     <property name="role">GtkFileChooserDialog</property>
     <property name="type-hint">dialog</property>
diff --git a/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.ui b/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.ui
index 9315717e79..a3027e22b5 100644
--- a/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.ui
+++ b/testsuite/tools/simplify-data-3to4/gtkfilechooserdialog.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface domain="gtk30">
-  <!-- interface-requires gtk+ 3.10 -->
   <template class="GtkFileChooserDialog" parent="GtkDialog">
     <property name="role">GtkFileChooserDialog</property>
     <property name="type-hint">dialog</property>
diff --git a/testsuite/tools/simplify-data-3to4/headerbar.expected b/testsuite/tools/simplify-data-3to4/headerbar.expected
index 5b642b28d8..c3ef9659de 100644
--- a/testsuite/tools/simplify-data-3to4/headerbar.expected
+++ b/testsuite/tools/simplify-data-3to4/headerbar.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="window1">
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">
diff --git a/testsuite/tools/simplify-data-3to4/headerbar.ui b/testsuite/tools/simplify-data-3to4/headerbar.ui
index c12d3d9ed1..07dc77e73d 100644
--- a/testsuite/tools/simplify-data-3to4/headerbar.ui
+++ b/testsuite/tools/simplify-data-3to4/headerbar.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">
diff --git a/testsuite/tools/simplify-data-3to4/nm-crash.expected b/testsuite/tools/simplify-data-3to4/nm-crash.expected
index a5b531f01a..a84ba689a6 100644
--- a/testsuite/tools/simplify-data-3to4/nm-crash.expected
+++ b/testsuite/tools/simplify-data-3to4/nm-crash.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface domain="nm-applet">
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkAssistant">
     <child>
       <object class="GtkAssistantPage">
diff --git a/testsuite/tools/simplify-data-3to4/notebook.expected b/testsuite/tools/simplify-data-3to4/notebook.expected
index f0bc7f9e82..b946bbaefd 100644
--- a/testsuite/tools/simplify-data-3to4/notebook.expected
+++ b/testsuite/tools/simplify-data-3to4/notebook.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="window1">
     <property name="child">
       <object class="GtkNotebook" id="notebook1">
diff --git a/testsuite/tools/simplify-data-3to4/notebook.ui b/testsuite/tools/simplify-data-3to4/notebook.ui
index ce3ce2cbad..ddf822beb8 100644
--- a/testsuite/tools/simplify-data-3to4/notebook.ui
+++ b/testsuite/tools/simplify-data-3to4/notebook.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkNotebook" id="notebook1">
diff --git a/testsuite/tools/simplify-data-3to4/office-runner.expected b/testsuite/tools/simplify-data-3to4/office-runner.expected
index d6860d0fd7..799691e703 100644
--- a/testsuite/tools/simplify-data-3to4/office-runner.expected
+++ b/testsuite/tools/simplify-data-3to4/office-runner.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="window1">
     <property name="border_width">12</property>
     <property name="title" translatable="yes">Office Runner</property>
diff --git a/testsuite/tools/simplify-data-3to4/office-runner.ui b/testsuite/tools/simplify-data-3to4/office-runner.ui
index 9f417cefbb..d7a7aae784 100644
--- a/testsuite/tools/simplify-data-3to4/office-runner.ui
+++ b/testsuite/tools/simplify-data-3to4/office-runner.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <property name="border_width">12</property>
     <property name="title" translatable="yes">Office Runner</property>
diff --git a/testsuite/tools/simplify-data-3to4/overlay.expected b/testsuite/tools/simplify-data-3to4/overlay.expected
index 67e6ccade1..095475de42 100644
--- a/testsuite/tools/simplify-data-3to4/overlay.expected
+++ b/testsuite/tools/simplify-data-3to4/overlay.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkOverlay">
     <child type="overlay">
       <object class="GtkButton" id="button">
diff --git a/testsuite/tools/simplify-data-3to4/paned.expected b/testsuite/tools/simplify-data-3to4/paned.expected
index a1acaae442..d767086ba8 100644
--- a/testsuite/tools/simplify-data-3to4/paned.expected
+++ b/testsuite/tools/simplify-data-3to4/paned.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkPaned">
     <property name="resize-end-child">0</property>
     <property name="shrink-start-child">0</property>
diff --git a/testsuite/tools/simplify-data-3to4/popover.expected b/testsuite/tools/simplify-data-3to4/popover.expected
index 9f2cafebc7..d204fdfe4d 100644
--- a/testsuite/tools/simplify-data-3to4/popover.expected
+++ b/testsuite/tools/simplify-data-3to4/popover.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkPopover" id="popover">
     <property name="autohide">0</property>
   </object>
diff --git a/testsuite/tools/simplify-data-3to4/scale.expected b/testsuite/tools/simplify-data-3to4/scale.expected
index 20e71ab9da..7a612ac8fe 100644
--- a/testsuite/tools/simplify-data-3to4/scale.expected
+++ b/testsuite/tools/simplify-data-3to4/scale.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkScale">
     <property name="draw-value">1</property>
     <property name="visible">0</property>
diff --git a/testsuite/tools/simplify-data-3to4/stack.expected b/testsuite/tools/simplify-data-3to4/stack.expected
index 611d20edf8..b8f1320c14 100644
--- a/testsuite/tools/simplify-data-3to4/stack.expected
+++ b/testsuite/tools/simplify-data-3to4/stack.expected
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="window1">
     <property name="child">
       <object class="GtkBox" id="box1">
diff --git a/testsuite/tools/simplify-data-3to4/stack.ui b/testsuite/tools/simplify-data-3to4/stack.ui
index e3133911ca..833d0d0a63 100644
--- a/testsuite/tools/simplify-data-3to4/stack.ui
+++ b/testsuite/tools/simplify-data-3to4/stack.ui
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <!-- interface-requires gtk+ 3.0 -->
   <object class="GtkWindow" id="window1">
     <child>
       <object class="GtkBox" id="box1">
diff --git a/testsuite/tools/simplify-data-3to4/toolbar.expected b/testsuite/tools/simplify-data-3to4/toolbar.expected
index fa090a9284..558022d325 100644
--- a/testsuite/tools/simplify-data-3to4/toolbar.expected
+++ b/testsuite/tools/simplify-data-3to4/toolbar.expected
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
-  <requires lib="gtk+" version="3.0"/>
+  <requires lib="gtk" version="4.0"/>
   <object class="GtkBox">
     <style>
       <class name="toolbar"/>
diff --git a/testsuite/tools/validate-data/invalid5.expected b/testsuite/tools/validate-data/invalid5.expected
new file mode 100644
index 0000000000..efe4d76422
--- /dev/null
+++ b/testsuite/tools/validate-data/invalid5.expected
@@ -0,0 +1 @@
+invalid5.ui:3:1 Required GTK version 5.10, current version is 3.99
diff --git a/testsuite/tools/validate-data/invalid5.ui b/testsuite/tools/validate-data/invalid5.ui
new file mode 100644
index 0000000000..f438790a4c
--- /dev/null
+++ b/testsuite/tools/validate-data/invalid5.ui
@@ -0,0 +1,3 @@
+<interface>
+  <requires lib="gtk" version="5.10"/>
+</interface>
diff --git a/testsuite/tools/validate-data/valid3.expected b/testsuite/tools/validate-data/valid3.expected
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/testsuite/tools/validate-data/valid3.ui b/testsuite/tools/validate-data/valid3.ui
new file mode 100644
index 0000000000..53d335aaec
--- /dev/null
+++ b/testsuite/tools/validate-data/valid3.ui
@@ -0,0 +1,5 @@
+<interface>
+  <requires lib="gtk" version="3.99"/>
+  <object class="GtkWindow">
+  </object>
+</interface>
diff --git a/testsuite/tools/validate-data/valid4.expected b/testsuite/tools/validate-data/valid4.expected
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/testsuite/tools/validate-data/valid4.ui b/testsuite/tools/validate-data/valid4.ui
new file mode 100644
index 0000000000..d913a7e598
--- /dev/null
+++ b/testsuite/tools/validate-data/valid4.ui
@@ -0,0 +1,5 @@
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <object class="GtkWindow">
+  </object>
+</interface>