1 files changed, 5 insertions, 0 deletions
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index e7bad62406..b18f3b38a6 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -419,6 +419,11 @@ class TestEnum(unittest.TestCase):
                 green = 2
                 blue = 3
 
+    def test_reserved__sunder_(self):
+        with self.assertRaisesRegex(ValueError, '_sunder_ names, such as '
+                                    '"_bad_", are reserved'):
+            class Bad(Enum):
+                _bad_ = 1
 
     def test_enum_with_value_name(self):
         class Huh(Enum):