diff --git a/sys/compat/linuxkpi/common/include/asm/atomic.h b/sys/compat/linuxkpi/common/include/asm/atomic.h
--- a/sys/compat/linuxkpi/common/include/asm/atomic.h
+++ b/sys/compat/linuxkpi/common/include/asm/atomic.h
@@ -218,6 +218,7 @@
 	__ret.val;							\
 })
 
+#define	cmpxchg64(...)		cmpxchg(__VA_ARGS__)
 #define	cmpxchg_relaxed(...)	cmpxchg(__VA_ARGS__)
 
 #define	xchg(ptr, new) ({						\