diff -r 84ef3c5b3698 -r 20d42311e344 lemon/bits/graph_extender.h
--- a/lemon/bits/graph_extender.h	Thu Feb 28 02:58:26 2008 +0000
+++ b/lemon/bits/graph_extender.h	Thu Feb 28 16:33:40 2008 +0000
@@ -20,6 +20,7 @@
 #define LEMON_BITS_GRAPH_EXTENDER_H
 
 #include <lemon/bits/invalid.h>
+#include <lemon/bits/utility.h>
 #include <lemon/error.h>
 
 #include <lemon/bits/map_extender.h>
@@ -330,10 +331,12 @@
   template <typename Base> 
   class UGraphExtender : public Base {
   public:
-    
+
     typedef Base Parent;
     typedef UGraphExtender Graph;
 
+    typedef True UndirectedTag;
+
     typedef typename Parent::Node Node;
     typedef typename Parent::Edge Edge;
     typedef typename Parent::UEdge UEdge;
@@ -753,6 +756,8 @@
     typedef Base Parent;
     typedef BpUGraphExtender Graph;
 
+    typedef True UndirectedTag;
+
     typedef typename Parent::Node Node;
     typedef typename Parent::ANode ANode;
     typedef typename Parent::BNode BNode;