diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 8bad157881d83bb262f582817760c19273ddef6b..11cea4105060dc8ddb1ffa8b26c4f46256c9b864 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -993,7 +993,7 @@ static void doSetupSDataBlock(SSqlRes* pRes, SSDataBlock* pBlock, void* pFilterI
         int32_t len = 0;
         taosMbsToUcs4(varDataVal(srcRow), varDataLen(srcRow), varDataVal(dstRow),
                       bytes-VARSTR_HEADER_SIZE, &len);
-        varDataLen(dstRow) = len;
+        varDataSetLen(dstRow, len);
       }
       memcpy(srcData, dstData, bytes*rows);
       free(dstData);