diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 65f95d797..2ea6d7c25 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -544,7 +544,7 @@ sweep_line_delete_edge (sweep_line_t *sweep, edge_t *edge)
 {
     if (edge->right != NULL) {
 	edge_t *next = edge->next;
-	if (next->x == edge->x) {
+	if (next && next->x == edge->x) {
 	    next->top = edge->top;
 	    next->right = edge->right;
 	} else
@@ -554,8 +554,8 @@ 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
@@ -564,10 +564,17 @@ sweep_line_delete (sweep_line_t	*sweep, rectangle_t *rectangle)
     cairo_bool_t update;
 
     update = TRUE;
-    if (sweep->fill_rule == CAIRO_FILL_RULE_WINDING &&
-	rectangle->left.prev->dir == rectangle->left.dir)
+
+    if (sweep->fill_rule == CAIRO_FILL_RULE_WINDING)
     {
-	update = rectangle->left.next != &rectangle->right;
+	if(rectangle->left.prev == NULL)
+	{
+	    update = FALSE; /* no change of direction */
+	}
+	else if(rectangle->left.prev->dir == rectangle->left.dir)
+	{
+	    update = rectangle->left.next != &rectangle->right; /* no right side, so no change of direction */
+	}
     }
 
     sweep_line_delete_edge (sweep, &rectangle->left);