diff --git a/Surface_mesh_segmentation/include/CGAL/internal/auxiliary/graph.h b/Surface_mesh_segmentation/include/CGAL/internal/auxiliary/graph.h
index 22b115a6595..8474a2d3b68 100644
--- a/Surface_mesh_segmentation/include/CGAL/internal/auxiliary/graph.h
+++ b/Surface_mesh_segmentation/include/CGAL/internal/auxiliary/graph.h
@@ -687,6 +687,8 @@ inline Graph::Graph(void (*err_function)(const char *))
   node_block_first = NULL;
   arc_for_block_first = NULL;
   arc_rev_block_first = NULL;
+  orphan_first = NULL;
+  orphan_last = NULL;
   flow = 0;
 }