(parameter) error: ValidationError Type 'undefined' cannot be used as an index type

I am trying to perform data validation using ValidationError from yup library so that I can show a custom validation error. But when I go through the inner error, it says the path type is undefined. What can I do to get it right?

import { ValidationError } from 'yup';

interface Errors {
    [key: string]: string;
}

export default function getValidationErrors(err: ValidationError): Errors {
    const validationErrors: Errors = {};

    err.inner.forEach(error => {
        validationErrors[error.path] = error.message;

    });
    return validationErrors;
}