Validate as NumberType but give choice via ChoiceType?

Question

symfony

It was

->add(
            'rating', // TODo - should be select with options from 1 to 5
            NumberType::class,
            [
                'attr' => [
                    'placeholder' => 'Rating',
                ],
            ]
        )

I would like to

->add(
            'rating',
            ChoiceType::class,
            [
                'choice_label' => 'Rating',
                'choices' => array(
                    'One' => 1,
                    'Two' => 2,
                    'Three' => 3,
                    'Four' => 4,
                    'Five' => 5,
                ),
            ]
        )

However, if it's an array, it throws an error

PropertyAccessor requires a graph of objects or arrays to operate on, but it found type "integer" while trying to traverse path "Rating" at property "Rating".

Because the accessor method returns numbers in essence

...
        $this->rating     = 0.0;
...

 /**
     * @return int
     */
    public function rating() : int
    {
        return $this->rating;
    }

    /**
     * @param int $rating
     */
    public function changeRating(int $rating) : void
    {
        $this->rating = $rating;
    }

How to render a form with a select, but validate the value as a number when submitting the form?