diff --git a/src/compositor/meta-window-group.c b/src/compositor/meta-window-group.c
index ee95c993c..2b423ea05 100644
--- a/src/compositor/meta-window-group.c
+++ b/src/compositor/meta-window-group.c
@@ -239,7 +239,7 @@ meta_window_group_paint (ClutterActor *actor)
       cairo_rectangle_int_t unredirected_rect;
       MetaWindow *window = meta_window_actor_get_meta_window (info->unredirected_window);
 
-      meta_window_get_outer_rect (window, &unredirected_rect);
+      meta_window_get_outer_rect (window, (MetaRectangle *)&unredirected_rect);
       cairo_region_subtract_rectangle (visible_region, &unredirected_rect);
     }