diff --git a/gtk/tools/gtk-builder-tool-simplify.c b/gtk/tools/gtk-builder-tool-simplify.c
index 72b867f920..5dc2464cc2 100644
--- a/gtk/tools/gtk-builder-tool-simplify.c
+++ b/gtk/tools/gtk-builder-tool-simplify.c
@@ -726,9 +726,12 @@ maybe_rename_property (Element *element, MyParserData *data)
     const char *new_name;
     const char *alt_names[3];
   } props[] = {
+    /* the "replacement" property is placed *after* the "added" properties */
     { "GtkPopover", "modal", GTK_TYPE_POPOVER, PROP_KIND_OBJECT, "autohide", { NULL, NULL, NULL } },
-    { "GtkWidget", "expand", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "hexpand", { "vexpand", NULL, NULL } },
-    { "GtkWidget", "margin", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "margin-left", { "margin-top", "margin-right", "margin-bottom" } },
+    { "GtkWidget", "expand", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "vexpand", { "hexpand", NULL, NULL } },
+    { "GtkWidget", "margin", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "margin-bottom", { "margin-start", "margin-end", "margin-top" } },
+    { "GtkWidget", "margin-left", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "margin-start", { NULL, NULL, NULL } },
+    { "GtkWidget", "margin-right", GTK_TYPE_WIDGET, PROP_KIND_OBJECT, "margin-end", { NULL, NULL, NULL } },
     { "GtkHeaderBar", "show-close-button", GTK_TYPE_HEADER_BAR, PROP_KIND_OBJECT, "show-title-buttons", { NULL, NULL, NULL } }
   };
   int i, k, l;
@@ -753,12 +756,12 @@ maybe_rename_property (Element *element, MyParserData *data)
 
   if (property_name == NULL)
     return;
- 
+
   type = g_type_from_name (class_name);
 
   canonical_name = g_strdup (property_name);
   g_strdelimit (canonical_name, "_", '-');
-  
+
   for (k = 0; k < G_N_ELEMENTS (props); k++)
     {
       if (g_type_is_a (type, props[k].type) &&
@@ -837,7 +840,7 @@ rewrite_stack_child (Element *child, MyParserData *data)
   prop->children = g_list_append (prop->children, object);
   prop->parent = new_object;
   new_object->children = g_list_append (new_object->children, prop);
-      
+
   g_list_free (child->children);
   child->children = g_list_append (NULL, new_object);
 
@@ -904,7 +907,7 @@ rewrite_assistant_child (Element *child, MyParserData *data)
   prop->children = g_list_append (prop->children, object);
   prop->parent = new_object;
   new_object->children = g_list_append (new_object->children, prop);
-      
+
   g_list_free (child->children);
   child->children = g_list_append (NULL, new_object);
 
@@ -1109,7 +1112,7 @@ rewrite_pack_type (Element *element,
     {
       Element *elt = l->data;
       if (g_str_equal (elt->element_name, "child"))
-        rewrite_pack_type_child (elt, data); 
+        rewrite_pack_type_child (elt, data);
     }
 }
 
@@ -1189,7 +1192,7 @@ rewrite_child_prop_to_prop (Element *element,
     {
       Element *elt = l->data;
       if (g_str_equal (elt->element_name, "child"))
-        rewrite_child_prop_to_prop_child (elt, data, child_prop, prop); 
+        rewrite_child_prop_to_prop_child (elt, data, child_prop, prop);
     }
 }
 
diff --git a/testsuite/tools/simplify-data-3to4/grid.expected b/testsuite/tools/simplify-data-3to4/grid.expected
index bf48a55268..61989d49f8 100644
--- a/testsuite/tools/simplify-data-3to4/grid.expected
+++ b/testsuite/tools/simplify-data-3to4/grid.expected
@@ -8,12 +8,12 @@
             <property name="label" translatable="yes">Hello World!</property>
             <property name="active">1</property>
             <property name="receives_default">1</property>
-            <property name="vexpand">1</property>
             <property name="hexpand">1</property>
+            <property name="vexpand">1</property>
+            <property name="margin-start">10</property>
+            <property name="margin-end">10</property>
             <property name="margin-top">10</property>
-            <property name="margin-right">10</property>
             <property name="margin-bottom">10</property>
-            <property name="margin-left">10</property>
             <layout>
               <property name="left_attach">0</property>
               <property name="top_attach">0</property>
diff --git a/testsuite/tools/simplify-data-3to4/office-runner.expected b/testsuite/tools/simplify-data-3to4/office-runner.expected
index 80d6e36587..9c0189733d 100644
--- a/testsuite/tools/simplify-data-3to4/office-runner.expected
+++ b/testsuite/tools/simplify-data-3to4/office-runner.expected
@@ -7,8 +7,8 @@
     <property name="window_position">center</property>
     <child>
       <object class="GtkBox" id="box1">
-        <property name="margin_left">12</property>
-        <property name="margin_right">12</property>
+        <property name="margin-start">12</property>
+        <property name="margin-end">12</property>
         <property name="margin_bottom">12</property>
         <property name="orientation">vertical</property>
         <property name="spacing">12</property>