diff --git a/Lib/enum.py b/Lib/enum.py
index 6e497f7ef6a..b50fe50d825 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -388,16 +388,8 @@ class _EnumDict(dict):
 
         Single underscore (sunder) names are reserved.
         """
-        if _is_internal_class(self._cls_name, value):
-            import warnings
-            warnings.warn(
-                    "In 3.13 classes created inside an enum will not become a member.  "
-                    "Use the `member` decorator to keep the current behavior.",
-                    DeprecationWarning,
-                    stacklevel=2,
-                    )
         if _is_private(self._cls_name, key):
-            # also do nothing, name will be a normal attribute
+            # do nothing, name will be a normal attribute
             pass
         elif _is_sunder(key):
             if key not in (
@@ -440,10 +432,9 @@ class _EnumDict(dict):
             value = value.value
         elif _is_descriptor(value):
             pass
-        # TODO: uncomment next three lines in 3.13
-        # elif _is_internal_class(self._cls_name, value):
-        #     # do nothing, name will be a normal attribute
-        #     pass
+        elif _is_internal_class(self._cls_name, value):
+            # do nothing, name will be a normal attribute
+            pass
         else:
             if key in self:
                 # enum overwriting a descriptor?
@@ -1169,28 +1160,13 @@ class Enum(metaclass=EnumType):
         if not last_values:
             return start
         try:
-            last = last_values[-1]
-            last_values.sort()
-            if last == last_values[-1]:
-                # no difference between old and new methods
-                return last + 1
-            else:
-                # trigger old method (with warning)
-                raise TypeError
+            last_value = sorted(last_values).pop()
         except TypeError:
-            import warnings
-            warnings.warn(
-                    "In 3.13 the default `auto()`/`_generate_next_value_` will require all values to be sortable and support adding +1\n"
-                    "and the value returned will be the largest value in the enum incremented by 1",
-                    DeprecationWarning,
-                    stacklevel=3,
-                    )
-            for v in last_values:
-                try:
-                    return v + 1
-                except TypeError:
-                    pass
-            return start
+            raise TypeError('unable to sort non-numeric values') from None
+        try:
+            return last_value + 1
+        except TypeError:
+            raise TypeError('unable to increment %r' % (last_value, )) from None
 
     @classmethod
     def _missing_(cls, value):
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 350554bfd2c..fe701025b70 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -1090,7 +1090,7 @@ class TestSpecial(unittest.TestCase):
             )
 
     @unittest.skipIf(
-            python_version < (3, 14),
+            python_version < (3, 13),
             'inner classes are still members',
             )
     def test_nested_classes_in_enum_are_not_members(self):
@@ -4261,21 +4261,21 @@ class TestInternals(unittest.TestCase):
         self.assertEqual(Color.green.value, 3)
 
     @unittest.skipIf(
-            python_version < (3, 14),
-            'mixed types with auto() will raise in the future',
+            python_version < (3, 13),
+            'mixed types with auto() will raise in 3.13',
             )
     def test_auto_garbage_fail(self):
-        with self.assertRaisesRegex(TypeError, 'will require all values to be sortable'):
+        with self.assertRaisesRegex(TypeError, "unable to increment 'red'"):
             class Color(Enum):
                 red = 'red'
                 blue = auto()
 
     @unittest.skipIf(
-            python_version < (3, 14),
-            'mixed types with auto() will raise in the future',
+            python_version < (3, 13),
+            'mixed types with auto() will raise in 3.13',
             )
     def test_auto_garbage_corrected_fail(self):
-        with self.assertRaisesRegex(TypeError, 'will require all values to be sortable'):
+        with self.assertRaisesRegex(TypeError, 'unable to sort non-numeric values'):
             class Color(Enum):
                 red = 'red'
                 blue = 2
@@ -4303,8 +4303,8 @@ class TestInternals(unittest.TestCase):
         self.assertEqual(Color.blue.value, 'blue')
 
     @unittest.skipIf(
-            python_version < (3, 14),
-            'auto() will return highest value + 1 in the future',
+            python_version < (3, 13),
+            'auto() will return highest value + 1 in 3.13',
             )
     def test_auto_with_aliases(self):
         class Color(Enum):