diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index 8ce116dc98e..2a57705622e 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -143,6 +143,7 @@
 #define	__dead2		__attribute__((__noreturn__))
 #define	__pure2		__attribute__((__const__))
 #define	__unused	__attribute__((__unused__))
+#define	__used		__attribute__((__used__))
 #define	__packed	__attribute__((__packed__))
 #define	__aligned(x)	__attribute__((__aligned__(x)))
 #define	__section(x)	__attribute__((__section__(x)))
@@ -151,6 +152,7 @@
 #define __dead2		__attribute__((__noreturn__))
 #define __pure2		__attribute__((__const__))
 #define __unused	__attribute__((__unused__))
+#define __used		__attribute__((__used__))
 #define __packed	__attribute__((__packed__))
 #define __aligned(x)	__attribute__((__aligned__(x)))
 #define __section(x)	__attribute__((__section__(x)))