diff --git a/include/boost/system/detail/config.hpp b/include/boost/system/detail/config.hpp
index f6ace68..296519b 100644
--- a/include/boost/system/detail/config.hpp
+++ b/include/boost/system/detail/config.hpp
@@ -60,6 +60,8 @@
 # endif
 #elif defined(_MSC_VER)
 #  define BOOST_SYSTEM_DEPRECATED(msg) __declspec(deprecated(msg))
+#else
+# define BOOST_SYSTEM_DEPRECATED(msg)
 #endif
 
 #endif // BOOST_SYSTEM_DETAIL_CONFIG_HPP_INCLUDED