setValues - TypeError: object of type 'int' has no len()

[ShuvalovEP]

Всем привет,
хотел воспроизвести, столкнулся с ошибкой

population, logbook = algorithms.eaSimple(population, toolbox,
                                        cxpb=P_CROSSOVER,
                                        mutpb=P_MUTATION,
                                        ngen=MAX_GENERATIONS,
                                        stats=stats,
                                        verbose=False) 

File "/Users/evgeny/projects/blue/venv/lib/python3.7/site-packages/deap/base.py", line 188, in setValues
    assert len(values) == len(self.weights), "Assigned values have not the same length than fitness weights"
TypeError: object of type 'int' has no len()

версия deap==1.3.1