Hello, Edward. First of all, thank you for correctly pointing out the problem. We'll integrate your patch but first I'd like to have a unit test that specifically shows why the secondonary `for` loop you introduced is necessary. Currently if we change this:

    for index, base in enumerate(mro[i + 1:], i + 1):
        if not issubclass(base, needle):
            break

to this:

    index = i + 1

the tests still pass.