diff -r 994c7df296c9 -r 1b89e29c9fc7 lemon/bits/edge_set_extender.h
--- a/lemon/bits/edge_set_extender.h	Thu Dec 10 17:05:35 2009 +0100
+++ b/lemon/bits/edge_set_extender.h	Thu Dec 10 17:18:25 2009 +0100
@@ -537,7 +537,7 @@
       typedef MapExtender<DefaultMap<Graph, Arc, _Value> > Parent;
 
     public:
-      ArcMap(const Graph& _g) 
+      explicit ArcMap(const Graph& _g) 
 	: Parent(_g) {}
       ArcMap(const Graph& _g, const _Value& _v) 
 	: Parent(_g, _v) {}
@@ -561,7 +561,7 @@
       typedef MapExtender<DefaultMap<Graph, Edge, _Value> > Parent;
 
     public:
-      EdgeMap(const Graph& _g) 
+      explicit EdgeMap(const Graph& _g) 
 	: Parent(_g) {}
 
       EdgeMap(const Graph& _g, const _Value& _v)