diff --git a/src/os_defs.h b/src/os_defs.h
index 82794f5..13539ee 100644
--- a/src/os_defs.h
+++ b/src/os_defs.h
@@ -109,6 +109,10 @@ typedef struct tagRECT {
 
 #define CONST const
 
+#ifndef __CONCAT
+	#define __CONCAT( a1, a2 ) a1 ## a2
+#endif
+
 #define __UNIQUENAME( a1, a2 )  __CONCAT( a1, a2 )
 #define UNIQUENAME( __text )    __UNIQUENAME( __text, __COUNTER__ )
 #define STATIC_ASSERT(e)  typedef char UNIQUENAME(STATIC_ASSERT_)[(e)?1:-1]