diff --git a/wenet/text/char_tokenizer.py b/wenet/text/char_tokenizer.py
index 5e47be41b..00b59b674 100644
--- a/wenet/text/char_tokenizer.py
+++ b/wenet/text/char_tokenizer.py
@@ -1,3 +1,5 @@
+import re
+
 from os import PathLike
 from typing import Dict, List, Optional, Union
 from wenet.utils.file_utils import read_symbol_table, read_non_lang_symbols