failed to pickle objects inherited from __slots__ in 1.2.2

[hotpxl]

My first test program is

class Base(object):
 __slots__ = []

class Inherited(Base):
 def __init__(self, v):
 self.v = v

import cloudpickle

a = Inherited(1)
with open("pickle", "wb") as f:
 cloudpickle.dump(a, f)

And then I read the pickle file with

import cloudpickle

with open("pickle", "rb") as f:
 cloudpickle.load(f)

When I run this with Python 3 and cloudpickle 1.2.2, it gives me error

Traceback (most recent call last):
 File "algo/code2.py", line 4, in <module>
 cloudpickle.load(f)
AttributeError: 'Inherited' object has no attribute '__dict__'

But this runs fine under Python 2 and cloudpickle 0.5.3