diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 8d061a1ce1..ed7c82a2dd 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -1511,11 +1511,13 @@ headerbar {
   }
 
   .solid-csd & {
-    margin-left: -1px;
-    margin-right: -1px;
-    margin-top: -1px;
-    border-radius: 0;
-    box-shadow: none;
+    &:backdrop, & {
+      margin-left: -1px;
+      margin-right: -1px;
+      margin-top: -1px;
+      border-radius: 0;
+      box-shadow: none;
+    }
   }
 }
 
diff --git a/gtk/theme/Adwaita/gtk-contained-dark.css b/gtk/theme/Adwaita/gtk-contained-dark.css
index a2de878260..e159f508d8 100644
--- a/gtk/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/theme/Adwaita/gtk-contained-dark.css
@@ -1929,7 +1929,8 @@ headerbar {
       min-width: 26px;
       margin: 0;
       padding: 0; }
-  .solid-csd .titlebar:not(headerbar), .solid-csd
+  .solid-csd .titlebar:backdrop:not(headerbar), .solid-csd .titlebar:not(headerbar), .solid-csd
+  headerbar:backdrop, .solid-csd
   headerbar {
     margin-left: -1px;
     margin-right: -1px;
diff --git a/gtk/theme/Adwaita/gtk-contained.css b/gtk/theme/Adwaita/gtk-contained.css
index e76ab44a10..c8496e80ec 100644
--- a/gtk/theme/Adwaita/gtk-contained.css
+++ b/gtk/theme/Adwaita/gtk-contained.css
@@ -1936,7 +1936,8 @@ headerbar {
       min-width: 26px;
       margin: 0;
       padding: 0; }
-  .solid-csd .titlebar:not(headerbar), .solid-csd
+  .solid-csd .titlebar:backdrop:not(headerbar), .solid-csd .titlebar:not(headerbar), .solid-csd
+  headerbar:backdrop, .solid-csd
   headerbar {
     margin-left: -1px;
     margin-right: -1px;