Issue #6477: Added support for pickling the types of built-in singletons.
diff --git a/Include/object.h b/Include/object.h
index 20c4780..5c89ca3 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -831,6 +831,9 @@
PyAPI_FUNC(void) Py_IncRef(PyObject *);
PyAPI_FUNC(void) Py_DecRef(PyObject *);
+PyAPI_DATA(PyTypeObject) PyNone_Type;
+PyAPI_DATA(PyTypeObject) PyNotImplemented_Type;
+
/*
_Py_NoneStruct is an object of undefined type which can be used in contexts
where NULL (nil) is not suitable (since NULL often means 'error').