diff --git a/include/boost/container_hash/hash_fwd.hpp b/include/boost/container_hash/hash_fwd.hpp
index 15d402f..6311d12 100644
--- a/include/boost/container_hash/hash_fwd.hpp
+++ b/include/boost/container_hash/hash_fwd.hpp
@@ -10,15 +10,26 @@
 
 namespace boost
 {
-    template <class T> struct hash;
 
-    template <class T> void hash_combine(std::size_t& seed, T const& v);
+namespace container_hash
+{
 
-    template <class It> std::size_t hash_range(It, It);
-    template <class It> void hash_range(std::size_t&, It, It);
+template<class T> struct is_range;
+template<class T> struct is_contiguous_range;
+template<class T> struct is_unordered_range;
 
-    template <class It> std::size_t hash_unordered_range(It, It);
-    template <class It> void hash_unordered_range(std::size_t&, It, It);
-}
+} // namespace container_hash
+
+template<class T> struct hash;
+
+template<class T> void hash_combine( std::size_t& seed, T const& v );
+
+template<class It> std::size_t hash_range( It, It );
+template<class It> void hash_range( std::size_t&, It, It );
+
+template<class It> std::size_t hash_unordered_range( It, It );
+template<class It> void hash_unordered_range( std::size_t&, It, It );
+
+} // namespace boost
 
 #endif // #ifndef BOOST_FUNCTIONAL_HASH_FWD_HPP