diff --git a/include/boost/optional/optional.hpp b/include/boost/optional/optional.hpp
index 47340b5..7219be0 100644
--- a/include/boost/optional/optional.hpp
+++ b/include/boost/optional/optional.hpp
@@ -133,7 +133,7 @@ class optional_base : public optional_tag
 {
   private :
 
-    typedef BOOST_DEDUCED_TYPENAME detail::make_reference_content<T>::type internal_type ;
+    typedef BOOST_DEDUCED_TYPENAME ::boost::detail::make_reference_content<T>::type internal_type ;
 
     typedef aligned_storage<internal_type> storage_type ;