--- a/musca.c
+++ b/musca.c
@@ -3202,7 +3202,7 @@ void mapnotify(XEvent *ev)
 		handle_map(ws);
 		head *h = head_by_root(ws->attr.root);
 		if (is_netwmstate(ws->state, NetWMStateFullscreen))
-			stack_push(h->fullscreen, (void*)ws);
+			stack_push(h->fullscreen, (void*)ws->w);
 		else
 		if (ws->attr.override_redirect || is_netwmstate(ws->state, NetWMStateAbove))
 			stack_push(h->above, (void*)ws->w);