diff --git a/src/cairo-polygon-intersect.c b/src/cairo-polygon-intersect.c
index 2cd73d2..1bd2646 100644
--- a/src/cairo-polygon-intersect.c
+++ b/src/cairo-polygon-intersect.c
@@ -1231,6 +1231,8 @@ active_edges (cairo_bo_edge_t		*left,
 	    } while (1);
 
 	    right = left->next;
+	    if (! right)
+		return;
 	    do {
 		if unlikely ((right->deferred.other))
 		    edges_end (right, top, polygon);
@@ -1243,6 +1245,8 @@ active_edges (cairo_bo_edge_t		*left,
 		}
 
 		right = right->next;
+		if (! right)
+		    return;
 	    } while (1);
 
 	    edges_start_or_continue (left, right, top, polygon);