diff --git a/src/zen/common/styles/zen-browser-ui.css b/src/zen/common/styles/zen-browser-ui.css
index a82d2b18..a8bdeda1 100644
--- a/src/zen/common/styles/zen-browser-ui.css
+++ b/src/zen/common/styles/zen-browser-ui.css
@@ -104,7 +104,7 @@
   #zen-main-app-wrapper,
   #zen-appcontent-wrapper,
   #zen-sidebar-splitter {
-    appearance: -moz-window-sidebar !important;
+    appearance: -moz-sidebar !important;
   }
 }