diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index 5fcf2bf485fc8a..f455da597f2441 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -12,6 +12,7 @@
 import contextlib
 import copy
 import cpp
+import enum
 import functools
 import hashlib
 import inspect
@@ -28,7 +29,7 @@
 
 from collections.abc import Callable
 from types import FunctionType, NoneType
-from typing import Any, NamedTuple, NoReturn, Literal, overload
+from typing import Any, Final, NamedTuple, NoReturn, Literal, overload
 
 # TODO:
 #
@@ -58,25 +59,22 @@
     "return_value",
 }
 
-class Unspecified:
-    def __repr__(self) -> str:
-        return '<Unspecified>'
-
-unspecified = Unspecified()
 
+class Sentinels(enum.Enum):
+    unspecified = "unspecified"
+    NULL = "null"
+    unknown = "unknown"
 
-class Null:
     def __repr__(self) -> str:
-        return '<Null>'
+        return f"<{self.value.capitalize()}>"
 
-NULL = Null()
 
+unspecified: Final = Sentinels.unspecified
+NULL: Final = Sentinels.NULL
+unknown: Final = Sentinels.unknown
 
-class Unknown:
-    def __repr__(self) -> str:
-        return '<Unknown>'
+NullType = type(Sentinels.NULL)
 
-unknown = Unknown()
 
 sig_end_marker = '--'
 
@@ -2600,7 +2598,7 @@ class CConverter(metaclass=CConverterAutoRegister):
     # Or the magic value "unknown" if this value is a cannot be evaluated
     # at Argument-Clinic-preprocessing time (but is presumed to be valid
     # at runtime).
-    default: bool | Unspecified = unspecified
+    default: bool | Literal[Sentinels.unspecified] = unspecified
 
     # If not None, default must be isinstance() of this type.
     # (You can also specify a tuple of types.)
@@ -2690,7 +2688,7 @@ def __init__(self,
              *,  # Keyword only args:
              c_default: str | None = None,
              py_default: str | None = None,
-             annotation: str | Unspecified = unspecified,
+             annotation: str | Literal[Sentinels.unspecified] = unspecified,
              unused: bool = False,
              **kwargs
     ):
@@ -2699,7 +2697,10 @@ def __init__(self,
         self.unused = unused
 
         if default is not unspecified:
-            if self.default_type and not isinstance(default, (self.default_type, Unknown)):
+            if (self.default_type
+                and default is not unknown
+                and not isinstance(default, self.default_type)
+            ):
                 if isinstance(self.default_type, type):
                     types_str = self.default_type.__name__
                 else:
@@ -3487,7 +3488,7 @@ def str_converter_key(types, encoding, zeroes):
 
 class str_converter(CConverter):
     type = 'const char *'
-    default_type = (str, Null, NoneType)
+    default_type = (str, NullType, NoneType)
     format_unit = 's'
 
     def converter_init(
@@ -3506,7 +3507,7 @@ def converter_init(
         self.format_unit = format_unit
         self.length = bool(zeroes)
         if encoding:
-            if self.default not in (Null, None, unspecified):
+            if self.default not in (NULL, None, unspecified):
                 fail("str_converter: Argument Clinic doesn't support default values for encoded strings")
             self.encoding = encoding
             self.type = 'char *'
@@ -3654,7 +3655,7 @@ def parse_arg(self, argname: str, displayname: str) -> str:
 
 class unicode_converter(CConverter):
     type = 'PyObject *'
-    default_type = (str, Null, NoneType)
+    default_type = (str, NullType, NoneType)
     format_unit = 'U'
 
     def parse_arg(self, argname: str, displayname: str) -> str:
@@ -3678,7 +3679,7 @@ def parse_arg(self, argname: str, displayname: str) -> str:
 @add_legacy_c_converter('Z#', accept={str, NoneType}, zeroes=True)
 class Py_UNICODE_converter(CConverter):
     type = 'const Py_UNICODE *'
-    default_type = (str, Null, NoneType)
+    default_type = (str, NullType, NoneType)
 
     def converter_init(
             self, *,