--- a/browser/themes/osx/devedition.css
+++ b/browser/themes/osx/devedition.css
@@ -65,19 +65,19 @@
   box-shadow: none;
 }
 
 /* Use forward-facing magnifying glass for the search box */
 .search-go-button {
   list-style-image: url("chrome://browser/skin/devedition/search.svg#search-icon-mac-inverted");
 }
 
-/* Don't use default colors when in full screen */
-#main-window:not([customizing]) #navigator-toolbox[inFullscreen] > #TabsToolbar:not(:-moz-lwtheme) {
-  -moz-appearance: none;
+/* Don't use the default background for tabs toolbar */
+#TabsToolbar {
+  -moz-appearance: none !important;
 }
 
 /* Tab styling - make sure to use an inverted icon for the selected tab
    (brighttext only covers the unselected tabs) */
 .tab-close-button[selected=true]:not(:hover) {
   -moz-image-region: rect(0, 64px, 16px, 48px);
 }
 @media (min-resolution: 2dppx) {