Issue #6477: Keep PyNotImplemented_Type and PyNone_Type private.
diff --git a/Include/object.h b/Include/object.h
index 5c89ca3..cdeb06c 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -831,8 +831,8 @@
PyAPI_FUNC(void) Py_IncRef(PyObject *);
PyAPI_FUNC(void) Py_DecRef(PyObject *);
-PyAPI_DATA(PyTypeObject) PyNone_Type;
-PyAPI_DATA(PyTypeObject) PyNotImplemented_Type;
+PyAPI_DATA(PyTypeObject) _PyNone_Type;
+PyAPI_DATA(PyTypeObject) _PyNotImplemented_Type;
/*
_Py_NoneStruct is an object of undefined type which can be used in contexts