diff --git a/source/client/src/clientImpl.c b/source/client/src/clientImpl.c
index 51e847d40c..790bb85fc3 100644
--- a/source/client/src/clientImpl.c
+++ b/source/client/src/clientImpl.c
@@ -1827,7 +1827,7 @@ static int32_t doConvertUCS4(SReqResultInfo* pResultInfo, int32_t numOfRows, int
           char* pStart = pCol->offset[j] + pCol->pData;
 
           int32_t len = taosUcs4ToMbsEx((TdUcs4*)varDataVal(pStart), varDataLen(pStart), varDataVal(p), conv);
-          if (len > bytes || (p + len) >= (pResultInfo->convertBuf[i] + colLength[i])) {
+          if (len < 0 || len > bytes || (p + len) >= (pResultInfo->convertBuf[i] + colLength[i])) {
             tscError(
                 "doConvertUCS4 error, invalid data. len:%d, bytes:%d, (p + len):%p, (pResultInfo->convertBuf[i] + "
                 "colLength[i]):%p",
@@ -2626,7 +2626,7 @@ static void fetchCallback(void* pResult, void* param, int32_t code) {
       setQueryResultFromRsp(pResultInfo, (const SRetrieveTableRsp*)pResultInfo->pData, pResultInfo->convertUcs4);
   if (pRequest->code != TSDB_CODE_SUCCESS) {
     pResultInfo->numOfRows = 0;
-    pRequest->code = code;
+    code = pRequest->code;
     tscError("0x%" PRIx64 " fetch results failed, code:%s, reqId:0x%" PRIx64, pRequest->self, tstrerror(code),
              pRequest->requestId);
   } else {