diff --git a/include/boost/utility/swap.hpp b/include/boost/utility/swap.hpp
index 952adf5..16750c8 100644
--- a/include/boost/utility/swap.hpp
+++ b/include/boost/utility/swap.hpp
@@ -38,8 +38,8 @@ namespace boost
 {
   namespace swap_adl_barrier
   {
-    template<class T>
-    void swap(T& left, T& right)
+    template<class T1, class T2>
+    void swap(T1& left, T2& right)
     {
       ::boost_swap_impl::swap_impl(left, right);
     }