diff --git a/include/boost/graph/detail/edge.hpp b/include/boost/graph/detail/edge.hpp
index badf28d4..3aba9f8d 100644
--- a/include/boost/graph/detail/edge.hpp
+++ b/include/boost/graph/detail/edge.hpp
@@ -13,6 +13,8 @@
 
 #include <iosfwd>
 
+#include <boost/functional/hash.hpp>
+
 namespace boost {
 
   namespace  detail {