diff --git a/src/encrypt.c b/src/encrypt.c
index 2064735d..27b1510e 100644
--- a/src/encrypt.c
+++ b/src/encrypt.c
@@ -1506,7 +1506,7 @@ int ss_check_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx)
     return 1;
 }
 
-void ss_gen_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx, int buf_size)
+char *ss_gen_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx, int buf_size)
 {
     int i, j;
     ssize_t blen = *buf_len;
@@ -1528,4 +1528,5 @@ void ss_gen_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx, in
     }
     *buf_len = j;
     *crc_idx = cidx;
+    return buf;
 }
diff --git a/src/encrypt.h b/src/encrypt.h
index b7b5a3a9..d2cf82f5 100644
--- a/src/encrypt.h
+++ b/src/encrypt.h
@@ -173,6 +173,6 @@ int ss_onetimeauth(char *auth, char *msg, int msg_len);
 int ss_onetimeauth_verify(char *auth, char *msg, int msg_len);
 
 int ss_check_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx);
-void ss_gen_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx, int buf_size);
+char * ss_gen_crc(char *buf, ssize_t *buf_len, char *crc_buf, ssize_t *crc_idx, int buf_size);
 
 #endif // _ENCRYPT_H
diff --git a/src/local.c b/src/local.c
index 34ec6601..0698a89f 100644
--- a/src/local.c
+++ b/src/local.c
@@ -245,7 +245,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
             }
 
             if (remote->send_ctx->connected && auth) {
-                ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
+                remote->buf = ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
             }
 
             // insert shadowsocks header
@@ -484,7 +484,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
                     memcpy(remote->buf, ss_addr_to_send, addr_len);
 
                     if (auth) {
-                        ss_gen_crc(buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
+                        buf = ss_gen_crc(buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
                     }
 
                     if (r > 0) {
diff --git a/src/redir.c b/src/redir.c
index 9a4c3852..d42d4eb7 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -185,7 +185,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
     }
 
     if (auth) {
-        ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
+        remote->buf = ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
     }
 
     remote->buf = ss_encrypt(BUF_SIZE, remote->buf, &r, server->e_ctx);
diff --git a/src/tunnel.c b/src/tunnel.c
index 6504a463..ad6cf13a 100644
--- a/src/tunnel.c
+++ b/src/tunnel.c
@@ -197,7 +197,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
     }
 
     if (auth) {
-        ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
+        remote->buf = ss_gen_crc(remote->buf, &r, remote->crc_buf, &remote->crc_idx, BUF_SIZE);
     }
 
     remote->buf = ss_encrypt(BUF_SIZE, remote->buf, &r, server->e_ctx);