diff --git a/lemon/bits/map_extender.h b/lemon/bits/map_extender.h
--- a/lemon/bits/map_extender.h
+++ b/lemon/bits/map_extender.h
@@ -49,6 +49,8 @@
     typedef typename Parent::Reference Reference;
     typedef typename Parent::ConstReference ConstReference;
 
+    typedef typename Parent::ReferenceMapTag ReferenceMapTag;
+
     class MapIt;
     class ConstMapIt;
 
@@ -191,6 +193,8 @@
     typedef typename Parent::Reference Reference;
     typedef typename Parent::ConstReference ConstReference;
 
+    typedef typename Parent::ReferenceMapTag ReferenceMapTag;
+
     class MapIt;
     class ConstMapIt;