diff --git a/include/boost/test/detail/config.hpp b/include/boost/test/detail/config.hpp
index 2d825b31ca..698b5d9961 100644
--- a/include/boost/test/detail/config.hpp
+++ b/include/boost/test/detail/config.hpp
@@ -136,7 +136,7 @@ class type_info;
 #define BOOST_PP_VARIADICS 1
 #endif
 
-#if BOOST_CLANG
+#ifdef BOOST_CLANG
 #define BOOST_PP_VARIADICS 1
 #endif