diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index b62d41c8213b6a3e258eaf0cc6480562ac52c9b7..fdafaaa07aa9344dbf58f3c9b347d935aacf7ad5 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -6094,6 +6094,7 @@ void tscPrintSelectClause(SSqlObj* pSql, int32_t subClauseIndex) {
   }
 
   str[offset] = ']';
+  assert(offset < totalBufSize);
   tscDebug("%p select clause:%s", pSql, str);
 }