diff --git a/include/boost/mpl/aux_/O1_size_impl.hpp b/include/boost/mpl/aux_/O1_size_impl.hpp
index 3bcbd0f..ad1ea06 100644
--- a/include/boost/mpl/aux_/O1_size_impl.hpp
+++ b/include/boost/mpl/aux_/O1_size_impl.hpp
@@ -29,8 +29,7 @@ namespace boost { namespace mpl {
 // member, and -1 otherwise; conrete sequences might override it by 
 // specializing either the 'O1_size_impl' or the primary 'O1_size' template
 
-#   if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) \
-    && !BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
+#   if !BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
 
 namespace aux {
 template< typename Sequence > struct O1_size_impl
@@ -69,7 +68,7 @@ struct O1_size_impl
     };
 };
 
-#   else // BOOST_MSVC
+#   else // __MWERKS__
 
 template< typename Tag >
 struct O1_size_impl