mypy: Cannot infer type argument 1 of "map"

When trying to check the following code using mypy:

import itertools
from typing import Sequence, Union, List
        
DigitsSequence = Union[str, Sequence[Union[str, int]]]


def normalize_input(digits: DigitsSequence) -> List[str]:
    try:
        new_digits = list(map(str, digits))  # <- Line 17
        if not all(map(str.isdecimal, new_digits)):
            raise TypeError
    except TypeError:
        print("Digits must be an iterable containing strings.")
        return []
    return new_digits

mypy throws the following errors:

calculate.py:17: error: Cannot infer type argument 1 of "map"

Why does this error occur? How can I fix it?

Thanks :)

Edit: It was actually a bug in mypy, and it's fixed now.