diff --git a/include/boost/regex/config.hpp b/include/boost/regex/config.hpp
index b67aaee4..24c13b25 100644
--- a/include/boost/regex/config.hpp
+++ b/include/boost/regex/config.hpp
@@ -119,7 +119,9 @@
 #define UNICODE
 #endif
 
-#define BOOST_REGEX_JOIN(x, y) x##y
+#define BOOST_REGEX_JOIN(X, Y) BOOST_REGEX_DO_JOIN(X, Y)
+#define BOOST_REGEX_DO_JOIN(X, Y) BOOST_REGEX_DO_JOIN2(X,Y)
+#define BOOST_REGEX_DO_JOIN2(X, Y) X##Y
 
 #ifdef BOOST_FALLTHROUGH
 #  define BOOST_REGEX_FALLTHROUGH BOOST_FALLTHROUGH