diff --git a/lemon/bellman_ford.h b/lemon/bellman_ford.h
--- a/lemon/bellman_ford.h
+++ b/lemon/bellman_ford.h
@@ -237,7 +237,9 @@
 	_local_dist = true;
 	_dist = Traits::createDistMap(*_gr);
       }
-      _mask = new MaskMap(*_gr, false);
+      if(!_mask) {
+        _mask = new MaskMap(*_gr);
+      }
     }
     
   public :
@@ -404,6 +406,10 @@
 	  _process.push_back(it);
 	  _mask->set(it, true);
 	}
+      } else {
+	for (NodeIt it(*_gr); it != INVALID; ++it) {
+	  _mask->set(it, false);
+	}
       }
     }