Volt is compiling wrong variable

My Phalcon web-app has worked for a long time. I did some changes the last week, and suddenly strange things happends with my templates.

app/config/services.php:

$di->set('view', function () use ($config, $di) {
    $view = new View();
    $view->core = new \stdClass;
    $view->core->breadcrumb = array();
});

BaseController.php:

public function appendBreadcrumb($url = false, $title = false, $fa_class = false) {
    if($url) $url = $this->di->getUrl()->get($url);
        $this->view->core->breadcrumb[] = array('url' => $url, 'title' => $title, 'class' => ($fa_class ? 'fa-'.$fa_class : false));
    }

mytemplate.volt:

{% if core.breadcrumb %}

The volt-file gets compiled to php-file with the variable "$this->core->breadcrumb". This variables is NULL. But when I change the php-file to "$core->breadcrumb" it works. Any hints to solve this problem?