diff --git a/lemon/smart_graph.h b/lemon/smart_graph.h
--- a/lemon/smart_graph.h
+++ b/lemon/smart_graph.h
@@ -73,7 +73,7 @@
       : nodes(_g.nodes), arcs(_g.arcs) { }
     
     typedef True NodeNumTag;
-    typedef True ArcNumTag;
+    typedef True EdgeNumTag;
 
     int nodeNum() const { return nodes.size(); }
     int arcNum() const { return arcs.size(); }