diff --git a/themes/base/jquery.ui.menu.css b/themes/base/jquery.ui.menu.css
index d53bdc6e0..b96d439ab 100644
--- a/themes/base/jquery.ui.menu.css
+++ b/themes/base/jquery.ui.menu.css
@@ -10,7 +10,7 @@
 .ui-menu { list-style:none; padding: 2px; margin: 0; display:block; outline: none; }
 .ui-menu .ui-menu { margin-top: -3px; position: absolute; }
 .ui-menu .ui-menu-item { margin: 0; padding: 0; zoom: 1; width: 100%; }
-.ui-menu .ui-menu-divider { margin: 5px -2px 5px -2px; height: 0; font-size: 0; line-height: 0; }
+.ui-menu .ui-menu-divider { margin: 5px -2px 5px -2px; height: 0; font-size: 0; line-height: 0; border-width: 1px 0 0 0; }
 .ui-menu .ui-menu-item a { text-decoration: none; display: block; padding: 2px .4em; line-height: 1.5; zoom: 1; font-weight: normal; }
 .ui-menu .ui-menu-item a.ui-state-focus,
 .ui-menu .ui-menu-item a.ui-state-active { font-weight: normal; margin: -1px; }