diff --git a/arch/x86/kernel/include/ihk/atomic.h b/arch/x86/kernel/include/ihk/atomic.h
index 7cb86d58..760c5f3f 100644
--- a/arch/x86/kernel/include/ihk/atomic.h
+++ b/arch/x86/kernel/include/ihk/atomic.h
@@ -165,7 +165,7 @@ static inline unsigned long atomic_cmpxchg8(unsigned long *addr,
 		unsigned long oldval,
 		unsigned long newval)
 {
-	asm volatile("lock; cmpxchgq %3, %1\n"
+	asm volatile("lock; cmpxchgq %2, %1\n"
 		     : "=a" (oldval), "+m" (*addr)
 		     : "r" (newval), "0" (oldval)
 		     : "memory"