diff --git a/include/boost/phoenix/stl/algorithm/detail/has_find.hpp b/include/boost/phoenix/stl/algorithm/detail/has_find.hpp
index cc6cf90..b089305 100644
--- a/include/boost/phoenix/stl/algorithm/detail/has_find.hpp
+++ b/include/boost/phoenix/stl/algorithm/detail/has_find.hpp
@@ -1,5 +1,7 @@
+///////////////////////////////////////////////////////////////////////////////
 // Copyright 2005 Daniel Wallin.
 // Copyright 2005 Joel de Guzman.
+// Copyright 2015 John Fletcher
 //
 // Use, modification and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -44,4 +46,7 @@ namespace boost
     };
 }
 
+// Bring in unordered_set and unordered_map stuff.
+#include "./is_unordered_set_or_map.hpp"
+
 #endif