diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
index 3493b8d..d28c024 100644
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -150,7 +150,7 @@
     def test_mode(self):
         self.test_write()
         f = gzip.GzipFile(self.filename, 'r')
-        self.assertTrue(f.myfileobj.mode.startswith('r'))
+        self.assertEqual(f.myfileobj.mode, 'rb')
         f.close()
 
     def test_1647484(self):