diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 5541bdc..fc8b1e9 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -554,8 +554,10 @@ sweep_line_delete_edge (sweep_line_t *sweep, edge_t *edge)
     if (sweep->cursor == edge)
 	sweep->cursor = edge->prev;
 
-    edge->prev->next = edge->next;
-    edge->next->prev = edge->prev;
+    if (edge->prev)
+        edge->prev->next = edge->next;
+    if (edge->next)
+        edge->next->prev = edge->prev;
 }
 
 static inline cairo_bool_t