Django 1.9.4: demo model fails, StateMachine has no attribute 'states'

[AlexPython]

Trying to run the the demo with Purchase model from readme.
python manange.py makemigrations ends with error:

File "django_states\machine.py", line 275, in get_state_choices
return [(k, cls.states[k].description) for k in cls.states.keys()] AttributeError: type object 'PurchaseSateMachine' has no attribute 'states'

Aren't class some_state (StateDefinition) inside class PurchaseStateMachine supposed to be states?

[treyd]

I have this same problem in django 1.11.6