diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 1b0591c6b824032b5f81aa74c855fb4728cda05f..65f49e315783c730a0af527f2d8ea9b7dbc0518b 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -2323,7 +2323,7 @@ void tscFirstRoundRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
                   tscError("stddev convert tag error:%d", ret);
                 }
               }else{
-                memcpy(p + offset, row[i], pExpr->base.resBytes);
+                memcpy(p + offset, row[i], length[i]);
               }
             }
             offset += pExpr->base.resBytes;