diff --git a/include/boost/config/compiler/clang_version.hpp b/include/boost/config/compiler/clang_version.hpp
index c0741e18..9e5b408a 100644
--- a/include/boost/config/compiler/clang_version.hpp
+++ b/include/boost/config/compiler/clang_version.hpp
@@ -2,7 +2,7 @@
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt)
 
-#if !defined(__APPLE)
+#if !defined(__APPLE__)
 
 # define BOOST_CLANG_VERSION (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__)