diff --git a/gtk-3.20/scss/apps/_unity.scss b/gtk-3.20/scss/apps/_unity.scss
index b7eb3b5..8a37aa1 100644
--- a/gtk-3.20/scss/apps/_unity.scss
+++ b/gtk-3.20/scss/apps/_unity.scss
@@ -42,7 +42,7 @@
         .left, .right, .bottom {
             background-color: $titlebar_bg_color;
 
-            &:backdrop { background-color: mix(shade($titlebar_bg_color, 0.7), $titlebar_fg_color, 0.21); }
+            &:backdrop { background-color: mix(shade($titlebar_bg_color, .7), $titlebar_fg_color, .21); }
         }
     }