diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 57c9890bdb..198690e5fb 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -4587,7 +4587,7 @@ decoration {
   .tiled-bottom &,
   .tiled-left & {
     border-radius: 0;
-    box-shadow: 0 0 0 1px $_wm_border_backdrop,
+    box-shadow: 0 0 0 1px $_wm_border,
                 0 0 0 20px transparent; //transparent control workaround -- #3670
 
     &:backdrop { box-shadow: 0 0 0 1px $_wm_border_backdrop,