--- edge_old.hpp	2015-02-11 17:35:46.808163000 +0100
+++ edge_new.hpp	2015-02-11 17:54:24.650109000 +0100
@@ -105,6 +105,8 @@
   }
 }
 
+#include <boost/functional/hash/hash.hpp>
+
 // Boost's functional/hash
 namespace boost {
   template<typename D, typename V>