diff --git a/include/boost/container_hash/extensions.hpp b/include/boost/container_hash/extensions.hpp
index 3636060..94adfa5 100644
--- a/include/boost/container_hash/extensions.hpp
+++ b/include/boost/container_hash/extensions.hpp
@@ -32,18 +32,6 @@
 
 namespace boost
 {
-    template <class A, class B>
-    std::size_t hash_value(std::pair<A, B> const&);
-
-    template <class A, class B>
-    std::size_t hash_value(std::pair<A, B> const& v)
-    {
-        std::size_t seed = 0;
-        boost::hash_combine(seed, v.first);
-        boost::hash_combine(seed, v.second);
-        return seed;
-    }
-
 #if !defined(BOOST_NO_CXX11_HDR_TUPLE)
     namespace hash_detail {
         template <std::size_t I, typename T>
diff --git a/include/boost/container_hash/hash.hpp b/include/boost/container_hash/hash.hpp
index d9e62cf..4ab436b 100644
--- a/include/boost/container_hash/hash.hpp
+++ b/include/boost/container_hash/hash.hpp
@@ -31,6 +31,7 @@
 #include <iterator>
 #include <string>
 #include <complex>
+#include <utility>
 #include <climits>
 
 #if !defined(BOOST_NO_CXX11_HDR_TYPEINDEX)
@@ -167,6 +168,19 @@ namespace boost
         return seed;
     }
 
+    // pair
+
+    template <class A, class B>
+    std::size_t hash_value( std::pair<A, B> const& v )
+    {
+        std::size_t seed = 0;
+
+        boost::hash_combine( seed, v.first );
+        boost::hash_combine( seed, v.second );
+
+        return seed;
+    }
+
     // ranges (list, set, deque...)
 
     template <typename T>