diff --git a/src/cairo-clip-boxes.c b/src/cairo-clip-boxes.c
index 16f5f7fc2..1c3f9403b 100644
--- a/src/cairo-clip-boxes.c
+++ b/src/cairo-clip-boxes.c
@@ -294,6 +294,7 @@ _cairo_clip_intersect_boxes (cairo_clip_t *clip,
 	if (clip->boxes != &clip->embedded_box)
 	    free (clip->boxes);
 
+	clip->boxes = NULL;
 	boxes = &clip_boxes;
     }