diff --git a/source/libs/sync/src/syncSnapshot.c b/source/libs/sync/src/syncSnapshot.c
index f060e9da13..2277b70c8f 100644
--- a/source/libs/sync/src/syncSnapshot.c
+++ b/source/libs/sync/src/syncSnapshot.c
@@ -1087,7 +1087,10 @@ static int32_t syncSnapSenderExchgSnapInfo(SSyncNode *pSyncNode, SSyncSnapshotSe
 
 // sender
 static int32_t syncNodeOnSnapshotPrepRsp(SSyncNode *pSyncNode, SSyncSnapshotSender *pSender, SyncSnapshotRsp *pMsg) {
+  int32_t   code = -1;
   SSnapshot snapshot = {0};
+
+  taosThreadMutexLock(&pSender->pSndBuf->mutex);
   pSyncNode->pFsm->FpGetSnapshotInfo(pSyncNode->pFsm, &snapshot);
 
   // prepare <begin, end>
@@ -1103,20 +1106,24 @@ static int32_t syncNodeOnSnapshotPrepRsp(SSyncNode *pSyncNode, SSyncSnapshotSend
   // start reader
   if (pMsg->payloadType == TDMT_SYNC_PREP_SNAPSHOT_REPLY) {
     if (syncSnapSenderExchgSnapInfo(pSyncNode, pSender, pMsg) != 0) {
-      return -1;
+      goto _out;
     }
   }
 
-  int32_t code = pSyncNode->pFsm->FpSnapshotStartRead(pSyncNode->pFsm, &pSender->snapshotParam, &pSender->pReader);
+  code = pSyncNode->pFsm->FpSnapshotStartRead(pSyncNode->pFsm, &pSender->snapshotParam, &pSender->pReader);
   if (code != 0) {
     sSError(pSender, "prepare snapshot failed since %s", terrstr());
-    return -1;
+    goto _out;
   }
 
   // update next index
   syncIndexMgrSetIndex(pSyncNode->pNextIndex, &pMsg->srcId, snapshot.lastApplyIndex + 1);
 
-  return snapshotSend(pSender);
+  code = snapshotSend(pSender);
+
+_out:
+  taosThreadMutexUnlock(&pSender->pSndBuf->mutex);
+  return code;
 }
 
 static int32_t snapshotSenderSignatureCmp(SSyncSnapshotSender *pSender, SyncSnapshotRsp *pMsg) {