Twig with ArrayAcess

I have a problem with dependency injection container and twig, I use Illuminate/Container:

// Register templates.
$this->singleton('templates', function ($c) {
    $twig = new \Twig_Environment(
        new \Twig_Loader_Filesystem([$c['paths.templates']]),
        [
            'debug' => true,
            // 'cache' => $c['paths.cache']
        ]
    );

    $twig->addExtension(new \Twig_Extension_Debug());

    $twig->addGlobal('app', $c['app']);

    return $twig;
});

$c['app'] is the container.

And in my template file I wanna access to my bindings:

{{ app.config.siteName }}

But that didn't work for me, I think it's a problem because the container implements to ArrayAcess