Pagination eror

Hi,

I've got a strange problem.

When I return this in my ForumController:

public function index()
{
    return Forum::with('topics')
        ->orderBy('created_at', 'DESC')
        ->paginate(10);
}

I receive the error:

Exception in JsonResponse.php line 65:
Failed calling Illuminate\P    agination\LengthAwarePaginator::jsonSerialize()
in JsonResponse.php line 65
at json_encode(array('forums' => object(LengthAwarePaginator)), '0') in JsonResponse.php line 65
at JsonResponse->setData(array('forums' => object(LengthAwarePaginator))) in JsonResponse.php line 50
at JsonResponse->__construct(array('forums' => object(LengthAwarePaginator)), '200', array()) in JsonResponse.php line 27
at JsonResponse->__construct(array('forums' => object(LengthAwarePaginator)), '200', array(), '0') in ResponseFactory.php line 83
at ResponseFactory->json(array('forums' => object(LengthAwarePaginator)), '200') in ForumController.php line 33

The url that for example:

forum.dev/forum?page=1

I've got lots of forum records in my database so it's not empty.

What could be going on?