diff --git a/include/boost/type_traits/config.hpp b/include/boost/type_traits/config.hpp
index c9fc08f..f19aaa7 100644
--- a/include/boost/type_traits/config.hpp
+++ b/include/boost/type_traits/config.hpp
@@ -25,7 +25,7 @@
 #   define BOOST_TT_DECL /**/
 #endif
 
-# if (defined(__MWERKS__) && __MWERKS__ >= 0x3000) || BOOST_MSVC > 1301 || defined(BOOST_NO_COMPILER_CONFIG)
+# if (defined(__MWERKS__) && __MWERKS__ >= 0x3000) || (defined(BOOST_MSVC) && (BOOST_MSVC > 1301)) || defined(BOOST_NO_COMPILER_CONFIG)
 #   define BOOST_TT_HAS_CONFORMING_IS_CLASS_IMPLEMENTATION
 #endif