diff --git a/Lib/idlelib/idle_test/test_macosx.py b/Lib/idlelib/idle_test/test_macosx.py
index b6bd922e4b9..19324773586 100644
--- a/Lib/idlelib/idle_test/test_macosx.py
+++ b/Lib/idlelib/idle_test/test_macosx.py
@@ -34,7 +34,7 @@ def test_init_sets_tktype(self):
         for platform, types in ('darwin', alltypes), ('other', nontypes):
             with self.subTest(platform=platform):
                 macosx.platform = platform
-                macosx._tk_type == None
+                macosx._tk_type = None
                 macosx._init_tk_type()
                 self.assertIn(macosx._tk_type, types)