diff --git a/include/boost/detail/reference_content.hpp b/include/boost/detail/reference_content.hpp
index 0dbcb4e..c93ea6f 100644
--- a/include/boost/detail/reference_content.hpp
+++ b/include/boost/detail/reference_content.hpp
@@ -18,12 +18,12 @@
 #   include "boost/type_traits/integral_constant.hpp"
 #   include "boost/type_traits/has_nothrow_copy.hpp"
 
-#include "boost/mpl/void.hpp"
-
 namespace boost {
 
 namespace detail {
 
+struct void_type {};
+
 ///////////////////////////////////////////////////////////////////////////////
 // (detail) class template reference_content
 //
@@ -71,7 +71,7 @@ public: // queries
 // Wraps with reference_content if specified type is reference.
 //
 
-template <typename T = mpl::void_> struct make_reference_content;
+template <typename T = void_type> struct make_reference_content;
 
 
 template <typename T>
@@ -88,7 +88,7 @@ struct make_reference_content< T& >
 
 
 template <>
-struct make_reference_content< mpl::void_ >
+struct make_reference_content< void_type >
 {
     template <typename T>
     struct apply
@@ -96,7 +96,7 @@ struct make_reference_content< mpl::void_ >
     {
     };
 
-    typedef mpl::void_ type;
+    typedef void_type type;
 };
 
 } // namespace detail