diff --git a/Lib/test/test_source_encoding.py b/Lib/test/test_source_encoding.py
index a285fc2ceef24e..36c8d87182dcf9 100644
--- a/Lib/test/test_source_encoding.py
+++ b/Lib/test/test_source_encoding.py
@@ -521,7 +521,7 @@ def check_script_error(self, src, expected, lineno=...):
             line = src.splitlines()[lineno-1].decode(errors='replace')
             if lineno == 1:
                 line = line.removeprefix('\ufeff')
-            line = line.encode(sys.stderr.encoding, sys.stderr.errors)
+            line = line.encode(sys.__stderr__.encoding, sys.__stderr__.errors)
             self.assertIn(line, err)