laravel5.1 firstOrFail() doesn't trigger 404

As far as I know using firstOrFail() in laravel5.1 without catching the exception results in a 404 error. My controller code:

 public function getTicket($id = null)
{
    $validator = Validator::make(compact('id'),[
        'id' => 'required|regex:/^[1-9]\d*$/',
    ]);

    if ($validator->fails()) 
       dd("no");

   $tickets = Auth::user()->tickets()->where('id', $id)->firstOrFail();

   dd($tickets);
}

When I use a not existing id of ticket I just get this error:

ModelNotFoundException in Builder.php line 157: No query results for model [App\ticket].

How to trigger a 404 error page? As laravel doc told me

If the exception is not caught, a 404 HTTP response is automatically sent back to the user[...]

this shoud be done in my case.laravel doc

via Chebli Mohamed