diff --git a/lemon/smart_graph.h b/lemon/smart_graph.h
--- a/lemon/smart_graph.h
+++ b/lemon/smart_graph.h
@@ -67,7 +67,7 @@
       : nodes(_g.nodes), arcs(_g.arcs) { }
 
     typedef True NodeNumTag;
-    typedef True EdgeNumTag;
+    typedef True ArcNumTag;
 
     int nodeNum() const { return nodes.size(); }
     int arcNum() const { return arcs.size(); }