title: Error while unserialization of model
body: <p>on my production system occurs an error while unserializing an user object within queue execution:</p>
  
  <pre><code>[2016-12-20 21:10:01] production.ERROR: Illuminate\Database\Eloquent\ModelNotFoundException: No query results for model [App\User]. in /var/www/virtual/bob/bobnet/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Builder.php:210
      Stack trace:
      #0 /var/www/virtual/bob/bobnet/vendor/laravel/framework/src/Illuminate/Queue/SerializesAndRestoresModelIdentifiers.php(45): Illuminate\Database\Eloquent\Builder-&gt;findOrFail(137)
  </code></pre>
  
  <p>If I run </p>
  
  <pre><code>\App\User::findOrFail(137)
  </code></pre>
  
  <p>the correct user could is found without an error. Until a few weeks everything worked fine. Just as the unserialization on my dev system.
  Has anyone an idea what's going wrong?</p>
  
  <p>Notification:</p>
  
  <pre><code>&lt;?php
  
  namespace App\Mail;
  
  use Carbon\Carbon;
  use Illuminate\Bus\Queueable;
  use Illuminate\Mail\Mailable;
  use Illuminate\Queue\SerializesModels;
  use Illuminate\Support\Facades\Mail;
  
  class GuideNotification extends Mailable
  {
      use Queueable, SerializesModels;
  
      // Once the data has been set to a public property, it will automatically be available in the view
      private $template;
      public $user;
      public $tour;
      public $pivot;
      public $sender;
      public $date;
  
      /**
       * Create a new message instance.
       *
       * @return void
       */
      public function __construct($template = 'emails.status_update', \App\User $user, \App\Tour $tour, $pivot, \App\User $sender = null)
      {
          $this-&gt;template = $template;
          $this-&gt;user     = $user;
          $this-&gt;tour     = $tour;
          $this-&gt;date     = new Carbon($tour-&gt;start);
          $this-&gt;pivot    = $pivot;
          if ($sender) {
              $this-&gt;sender = $sender-&gt;fullName();
          }
  
      }
  
      /**
       * Build the message.
       *
       * @return $this
       */
      public function build()
      {
          return $this
              -&gt;to($this-&gt;user-&gt;email)
              -&gt;cc(config('bob.bcc_mail'), 'BoB')
              -&gt;subject($this-&gt;generateSubject())
              -&gt;view($this-&gt;template);
      }
  
      protected function generateSubject()
      {
          switch ($this-&gt;template) {
              case 'emails.request':
                  return 'Guide Anfrage ' . $this-&gt;tour-&gt;name . ' am ' . $this-&gt;date-&gt;format('d.m.Y') . ' um ' . $this-&gt;date-&gt;format('H:i') . ' Uhr (ID ' . $this-&gt;tour-&gt;id . ')';
                  break;
              case 'emails.confirmation':
                  return 'Guide Bestätigung ' . $this-&gt;tour-&gt;name . ' am ' . $this-&gt;date-&gt;format('d.m.Y') . ' um ' . $this-&gt;date-&gt;format('H:i') . ' Uhr (ID ' . $this-&gt;tour-&gt;id . ')';
                  break;
              case 'emails.change':
                  return 'Guide Änderung ' . $this-&gt;tour-&gt;name . ' am ' . $this-&gt;date-&gt;format('d.m.Y') . ' um ' . $this-&gt;date-&gt;format('H:i') . ' Uhr (ID ' . $this-&gt;tour-&gt;id . ')';
                  break;
              case 'emails.freesale':
                  return 'Guide Bestätigung "geschnappte" ' . $this-&gt;tour-&gt;name . ' am ' . $this-&gt;date-&gt;format('d.m.Y') . ' um ' . $this-&gt;date-&gt;format('H:i') . ' Uhr (ID ' . $this-&gt;tour-&gt;id . ')';
                  break;
              default:
                  return 'Guide Statusupdate ' . $this-&gt;tour-&gt;name . ' am ' . $this-&gt;date-&gt;format('d.m.Y') . ' um ' . $this-&gt;date-&gt;format('H:i') . ' Uhr (ID ' . $this-&gt;tour-&gt;id . ')';
                  break;
          }
      }
  }
  </code></pre>