diff --git a/src/thread/x86_64/syscall_cp.s b/src/thread/x86_64/syscall_cp.s
index 8b250488..9727ad3d 100644
--- a/src/thread/x86_64/syscall_cp.s
+++ b/src/thread/x86_64/syscall_cp.s
@@ -19,7 +19,7 @@ __syscall_cp_asm:
 	mov %r11,8(%rsp)
 1:	syscall
 	xor %ecx,%ecx
-	mov 8(%rsp),%edi
+	mov 8(%rsp),%rdi
 	mov %rcx,(%rdi)
 	ret
 2:	call __cancel