diff --git a/codespell_lib/_codespell.py b/codespell_lib/_codespell.py
index f2c6c44cb66..3545e258689 100644
--- a/codespell_lib/_codespell.py
+++ b/codespell_lib/_codespell.py
@@ -19,6 +19,7 @@
 import argparse
 import configparser
 import fnmatch
+import locale
 import os
 import re
 import sys
@@ -228,7 +229,8 @@ def open_with_chardet(self, filename: str) -> Tuple[List[str], str]:
                     break
         self.encdetector.close()
         encoding = self.encdetector.result["encoding"]
-        assert encoding is not None  # noqa: S101
+        if not encoding:
+            encoding = locale.getpreferredencoding(False)
 
         try:
             f = open(filename, encoding=encoding, newline="")