diff --git a/mozilla/xpfe/global/resources/skin/xul.css b/mozilla/xpfe/global/resources/skin/xul.css
index b78e1ca97f4..7edcffb652c 100644
--- a/mozilla/xpfe/global/resources/skin/xul.css
+++ b/mozilla/xpfe/global/resources/skin/xul.css
@@ -277,7 +277,7 @@ xpmenu {
 
 
 /* xpmenu visibility rules */
--moz-dropdown-menu {
+:-moz-dropdown-menu {
   background-color:inherit;
   color: inherit;
   border: 1px white outset;