diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 201f40a..1607c62 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -94,7 +94,8 @@
 
 #if defined(__STDC__) || defined(__cplusplus)
 #define	__P(protos)	protos		/* full-blown ANSI C */
-#define	__CONCAT(x,y)	x ## y
+#define	__CONCAT1(x,y)	x ## y
+#define	__CONCAT(x,y)	__CONCAT1(x,y)
 #define	__STRING(x)	#x
 
 #if defined(__cplusplus)