diff --git a/codespell_lib/_codespell.py b/codespell_lib/_codespell.py
index f2c6c44cb6..baf77997af 100644
--- a/codespell_lib/_codespell.py
+++ b/codespell_lib/_codespell.py
@@ -228,7 +228,6 @@ 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
 
         try:
             f = open(filename, encoding=encoding, newline="")
@@ -245,7 +244,7 @@ def open_with_chardet(self, filename: str) -> Tuple[List[str], str]:
             lines = f.readlines()
             f.close()
 
-        return lines, encoding
+        return lines, f.encoding
 
     def open_with_internal(self, filename: str) -> Tuple[List[str], str]:
         encoding = None
diff --git a/codespell_lib/tests/test_basic.py b/codespell_lib/tests/test_basic.py
index 7a36369bf9..d7bd72de9e 100644
--- a/codespell_lib/tests/test_basic.py
+++ b/codespell_lib/tests/test_basic.py
@@ -384,6 +384,16 @@ def test_encoding(
     assert "WARNING: Binary file" in stderr
 
 
+def test_unknown_encoding_chardet(
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test opening a file with unknown encoding using chardet"""
+    fname = tmp_path / "tmp"
+    fname.touch()
+    assert cs.main("--hard-encoding-detection", fname) == 0
+
+
 def test_ignore(
     tmp_path: Path,
     capsys: pytest.CaptureFixture[str],