Declaration of App\PostRoute::match(Nette\Http\IRequest $httpRequest) must be compatible

Ahojte,
přešel jsem na Nette 3 a začala mi to u routování hlásit:

Declaration of App\PostRoute::match(Nette\Http\IRequest $httpRequest) must be compatible with Nette\Application\Routers\Route::match(Nette\Http\IRequest $httpRequest): ?array

<?php
namespace App;

use Nette;
use App\Model\PostManager;

class PostRoute extends \Nette\Application\Routers\Route
{

    /** @var PostManager @inject */
    public $postManager;

    public function match(Nette\Http\IRequest $httpRequest)
    {
        $appRequest = parent::match($httpRequest);
        if (!isset($appRequest->parameters['id'])) {
            return null;
        }
        $id = $appRequest->parameters['id'];
        if (!is_numeric($id)) {
            $post = null;
            try {
                $post = $this->postManager->getPosts()->get($id)->slug;
            } catch (Nette\Application\BadRequestException $exc) {
                return null;
            }
            $appRequest->parameters['id'] = $post->id;
        }
        return $appRequest;
    }
}

?>

Jak by to mělo prosím správně vypadat? Děkuji