diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 65f95d797..5bca289cd 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -468,6 +468,9 @@ active_edges_to_traps (sweep_line_t *sweep)
 	    edge_t *left, *right;
 	    int winding;
 
+	    if (unlikely (pos == NULL))
+		break;
+
 	    left = pos;
 	    winding = left->dir;
 
@@ -503,6 +506,8 @@ active_edges_to_traps (sweep_line_t *sweep)
 		 * boxes.
 		 */
 		winding += right->dir;
+		if (unlikely (right->next == NULL))
+	            break;
 		if (winding == 0 && right->x != right->next->x)
 		    break;