Index: wp-admin/css/wp-admin.css
===================================================================
--- wp-admin/css/wp-admin.css	(revision 22974)
+++ wp-admin/css/wp-admin.css	(working copy)
@@ -5605,7 +5605,7 @@
 }
 
 /* Collapse Button */
-.wp-full-overlay .collapse-sidebar {
+.wp-full-overlay a.collapse-sidebar {
 	position: absolute;
 	bottom: 12px;
 	left: 0;