Index: src/wp-admin/css/admin-menu.css
===================================================================
--- src/wp-admin/css/admin-menu.css	(revision 38274)
+++ src/wp-admin/css/admin-menu.css	(working copy)
@@ -485,7 +485,8 @@
 }
 
 #adminmenu li.menu-top:hover .wp-menu-image img,
-#adminmenu li.wp-has-current-submenu .wp-menu-image img {
+#adminmenu li.wp-has-current-submenu .wp-menu-image img,
+#adminmenu li.menu-top.current .wp-menu-image img {
 	opacity: 1;
 	filter: alpha(opacity=100);
 }