diff --git a/gtk/resources/theme/Adwaita/_common.scss b/gtk/resources/theme/Adwaita/_common.scss
index 0107b492b3..a122bd03cf 100644
--- a/gtk/resources/theme/Adwaita/_common.scss
+++ b/gtk/resources/theme/Adwaita/_common.scss
@@ -149,14 +149,21 @@ GtkLabel {
 }
 
 GtkAssistant {
-  & .sidebar {
+  .sidebar {
     background-color: $base_color;
+    border-right: 1px solid $borders_color;
+    border-top: 1px solid $borders_color;
+    &:backdrop {
+      background-color: $backdrop_base_color;
+      border-color: $backdrop_borders_color;
+    }
   }
-  & .sidebar GtkLabel {
-    padding: 6px;
+  &.csd .sidebar { border-top-style: none; }
+  .sidebar GtkLabel {
+    padding: 6px 12px;
   }
-  & .sidebar GtkLabel.highlight {
-    background-color: darken($bg_color, 10%);
+  .sidebar GtkLabel.highlight {
+    background-color: mix($bg_color, $fg_color, 80%);
   }
 }
 
diff --git a/gtk/resources/theme/Adwaita/gtk-contained-dark.css b/gtk/resources/theme/Adwaita/gtk-contained-dark.css
index 01f4b7af6a..c557d06691 100644
--- a/gtk/resources/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/resources/theme/Adwaita/gtk-contained-dark.css
@@ -125,11 +125,18 @@ GtkLabel:insensitive {
   text-shadow: none; }
 
 GtkAssistant .sidebar {
-  background-color: #292929; }
+  background-color: #292929;
+  border-right: 1px solid #1c1f1f;
+  border-top: 1px solid #1c1f1f; }
+  GtkAssistant .sidebar:backdrop {
+    background-color: #2c2c2c;
+    border-color: #1e2222; }
+GtkAssistant.csd .sidebar {
+  border-top-style: none; }
 GtkAssistant .sidebar GtkLabel {
-  padding: 6px; }
+  padding: 6px 12px; }
 GtkAssistant .sidebar GtkLabel.highlight {
-  background-color: #212424; }
+  background-color: #5d6261; }
 
 .app-notification.frame, .osd {
   color: #eeeeec;
diff --git a/gtk/resources/theme/Adwaita/gtk-contained.css b/gtk/resources/theme/Adwaita/gtk-contained.css
index 5f7faa3680..da81f34816 100644
--- a/gtk/resources/theme/Adwaita/gtk-contained.css
+++ b/gtk/resources/theme/Adwaita/gtk-contained.css
@@ -125,11 +125,18 @@ GtkLabel:insensitive {
   text-shadow: none; }
 
 GtkAssistant .sidebar {
-  background-color: #ffffff; }
+  background-color: #ffffff;
+  border-right: 1px solid #a1a1a1;
+  border-top: 1px solid #a1a1a1; }
+  GtkAssistant .sidebar:backdrop {
+    background-color: #fcfcfc;
+    border-color: #a8a8a8; }
+GtkAssistant.csd .sidebar {
+  border-top-style: none; }
 GtkAssistant .sidebar GtkLabel {
-  padding: 6px; }
+  padding: 6px 12px; }
 GtkAssistant .sidebar GtkLabel.highlight {
-  background-color: lightgray; }
+  background-color: #c6c8c8; }
 
 .app-notification.frame, .osd {
   color: #eeeeec;