PHP Spatie DTOs with sub arrays

I'm trying to implement an endpoint for the Audd audio detection API (callback with a result), using Spatie's Data Transfer Object package for PHP. For this, I have a PlayDTO, which has a PlayResultDTO attribute, which in turn should have an array of PlayTrackDTOs as a sub-attribute:

// PlayDTO.php
namespace App\DTO\Play;
use Spatie\DataTransferObject\DataTransferObject;

class PlayDTO extends DataTransferObject
{
    public string $status;
    public PlayResultDTO $result;
}

//PlayResultDTO.php
namespace App\DTO\Play;
use Spatie\DataTransferObject\DataTransferObject;
class PlayResultDTO extends DataTransferObject
{
    public int $radio_id;
    public string $timestamp;
    public int $play_length;
    /** @var PlayTrackDTO[] */
    #[CastWith(ArrayCaster::class, itemType: PlayTrackDTO::class)]
    public array $results;
}

// PlayTrackDTO.php
namespace App\DTO\Play;
use Spatie\DataTransferObject\DataTransferObject;
class PlayTrackDTO extends DataTransferObject
{
    public string $artist;
    public string $title;
    public string $album;
    public string $release_date;
    public string $label;
    public int $score;
    public string $song_link;
}

When I pass a valid array of data to my PlayDTO constructor, in the newly instaitated PlayDTO class, $result correctly has type PlayResultDTO, but in that $result it's $results attribute is just a simple array of keyed-arrays, when it should be an array of PlayTrackDTO objects.

As far as I can see I followed the guide correctly. I have the most up to date version of the package installed, as well as using PHP8. Would anyone have any suggestions? Thanks

You need to use the CastWith class form Spatie Attributes. Also, you are using ArrayCaster, so you need to use that as well.

use Spatie\DataTransferObject\Casters\ArrayCaster;
use Spatie\DataTransferObject\Attributes\CastWith;