diff --git a/tests/test_igzip.py b/tests/test_igzip.py
index b31adb85..1cd9517e 100644
--- a/tests/test_igzip.py
+++ b/tests/test_igzip.py
@@ -387,7 +387,7 @@ def test_compress_infile_out_file_no_name(monkeypatch, tmp_path, capsysbinary):
     assert gzip.decompress(output) == DATA
     assert err == b''
     assert out == b''
-    assert output[4] & gzip.FNAME == 0  # No filename set.
+    assert output[3] & gzip.FNAME == 0  # No filename set.
     assert output[4:8] == b"\x00\x00\x00\x00"  # No timestamp set.