diff --git a/include/boost/system/detail/system_category_win32.hpp b/include/boost/system/detail/system_category_win32.hpp
index 2035678..4739b89 100644
--- a/include/boost/system/detail/system_category_win32.hpp
+++ b/include/boost/system/detail/system_category_win32.hpp
@@ -26,7 +26,7 @@ namespace system
 namespace detail
 {
 
-#if defined(_MSC_VER) && _MSC_VER < 1900
+#if ( defined(_MSC_VER) && _MSC_VER < 1900 ) || ( defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) )
 
 inline char const * unknown_message_win32( int ev, char * buffer, std::size_t len )
 {