Index: wp-admin/css/wp-admin.css
===================================================================
--- wp-admin/css/wp-admin.css	(revision 26731)
+++ wp-admin/css/wp-admin.css	(working copy)
@@ -1920,7 +1920,7 @@
 /* Sticky admin menu */
 .sticky-menu #adminmenuwrap {
 	position: fixed;
-	z-index: 99; /* Match the z-index of .wp-submenu to ensure flyout menus don't appear underneath main column elements */
+	z-index: 999; /* Match the z-index of .wp-submenu to ensure flyout menus don't appear underneath main column elements */
 }
 
 /* A new arrow */