diff --git a/include/gmssl/sm4_cbc_mac.h b/include/gmssl/sm4_cbc_mac.h
index e803c8d7..26deb18c 100644
--- a/include/gmssl/sm4_cbc_mac.h
+++ b/include/gmssl/sm4_cbc_mac.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
+ *  Copyright 2014-2023 The GmSSL Project. All Rights Reserved.
  *
  *  Licensed under the Apache License, Version 2.0 (the License); you may
  *  not use this file except in compliance with the License.
@@ -24,6 +24,8 @@ typedef struct {
 	size_t ivlen;
 } SM4_CBC_MAC_CTX;
 
+#define SM4_CBC_MAC_SIZE	(SM4_BLOCK_SIZE)
+
 void sm4_cbc_mac_init(SM4_CBC_MAC_CTX *ctx, const uint8_t key[16]);
 void sm4_cbc_mac_update(SM4_CBC_MAC_CTX *ctx, const uint8_t *data, size_t datalen);
 void sm4_cbc_mac_finish(SM4_CBC_MAC_CTX *ctx, uint8_t mac[16]);