diff --git a/src/win.c b/src/win.c
index fb61191638..502bb82a63 100644
--- a/src/win.c
+++ b/src/win.c
@@ -350,7 +350,7 @@ bool win_bind_mask(struct backend_base *b, struct managed_win *w) {
 	auto reg_bound_local = win_get_bounding_shape_global_by_val(w);
 	pixman_region32_translate(&reg_bound_local, -w->g.x, -w->g.y);
 	w->mask_image = b->ops->make_mask(
-	    b, (geometry_t){.width = w->g.width, .height = w->g.height}, &reg_bound_local);
+	    b, (geometry_t){.width = w->widthb, .height = w->heightb}, &reg_bound_local);
 	pixman_region32_fini(&reg_bound_local);
 
 	if (!w->mask_image) {