diff --git a/src/backend/graph.cpp b/src/backend/graph.cpp
index 7933309b..64a690f5 100644
--- a/src/backend/graph.cpp
+++ b/src/backend/graph.cpp
@@ -255,7 +255,6 @@ namespace boss {
                         boost::add_edge(parentVertex, vertex, graph);
                     }
                 }
-                ++vit2;
             }
         }
     }