diff --git a/gtk/resources/theme/Adwaita/_common.scss b/gtk/resources/theme/Adwaita/_common.scss
index 0a4f8c43c0..a98a699d15 100644
--- a/gtk/resources/theme/Adwaita/_common.scss
+++ b/gtk/resources/theme/Adwaita/_common.scss
@@ -735,6 +735,11 @@ GtkComboBox {
         &:backdrop:insensitive { @include button($t:backdrop-insensitive, $noedge:true); }
       }
     }
+    .selection-menu {
+      border-width: 0;
+      background-image: none;
+      box-shadow: none;
+    }
   }
   .tiled &, .maximized & {
     border-radius: 0; // squared corners when the window is max'd or tiled
diff --git a/gtk/resources/theme/Adwaita/gtk-contained-dark.css b/gtk/resources/theme/Adwaita/gtk-contained-dark.css
index 319760063b..0d501583bd 100644
--- a/gtk/resources/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/resources/theme/Adwaita/gtk-contained-dark.css
@@ -978,6 +978,11 @@ GtkComboBox {
           border-color: #1e2222;
           background-image: linear-gradient(to bottom, #393f3f);
           box-shadow: inset 0 1px rgba(255, 255, 255, 0); }
+    .titlebar.selection-mode .selection-menu,
+    .header-bar.selection-mode .selection-menu {
+      border-width: 0;
+      background-image: none;
+      box-shadow: none; }
   .tiled .titlebar, .maximized .titlebar, .tiled
   .header-bar, .maximized
   .header-bar {
diff --git a/gtk/resources/theme/Adwaita/gtk-contained.css b/gtk/resources/theme/Adwaita/gtk-contained.css
index 0a8875a4c9..d6df0e9de1 100644
--- a/gtk/resources/theme/Adwaita/gtk-contained.css
+++ b/gtk/resources/theme/Adwaita/gtk-contained.css
@@ -970,6 +970,11 @@ GtkComboBox {
           border-color: #a8a8a8;
           background-image: linear-gradient(to bottom, #ededed);
           box-shadow: inset 0 1px rgba(255, 255, 255, 0); }
+    .titlebar.selection-mode .selection-menu,
+    .header-bar.selection-mode .selection-menu {
+      border-width: 0;
+      background-image: none;
+      box-shadow: none; }
   .tiled .titlebar, .maximized .titlebar, .tiled
   .header-bar, .maximized
   .header-bar {