diff --git a/themes/base/jquery.ui.menu.css b/themes/base/jquery.ui.menu.css
index 7970422c7a6..719b426465f 100644
--- a/themes/base/jquery.ui.menu.css
+++ b/themes/base/jquery.ui.menu.css
@@ -25,7 +25,7 @@
 	cursor: pointer;
 	min-height: 0; /* support: IE7 */
 	/* support: IE10, see #8844 */
-	list-style-image: url(data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7);
+	list-style-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
 }
 .ui-menu .ui-menu-divider {
 	margin: 5px 0;