diff --git a/wenet/utils/file_utils.py b/wenet/utils/file_utils.py
index 0444c1ac2f..aadf1095b2 100644
--- a/wenet/utils/file_utils.py
+++ b/wenet/utils/file_utils.py
@@ -39,7 +39,7 @@ def read_non_lang_symbols(non_lang_sym_path):
 
     """
     if non_lang_sym_path is None:
-        return {}
+        return None
     else:
         syms = read_lists(non_lang_sym_path)
         non_lang_syms_pattern = re.compile(r"(\[[^\[\]]+\]|<[^<>]+>|{[^{}]+})")