Symfony2 Variable "name" does not exist

Symfony2 Variable "name" does not exist

I'm new to Symfony, so this is most certain a simple mistake from my side.
I get the following error: Variable "worker" does not exist.
The template looks like this:
{% extends "NTSBSServiceBundle::layout.html.twig" %}
{% block body %}
<h1>Rapportera</h1>
{% for worker in workers if workers %}
{{ worker.name }}
{% else %}
<em>Det finns inga öppna protokoll för närvarande...</em>
{% endfor %}
{% endblock %}
And the controller method look like this:
/**
* List all open protocols, grouped by worker.
*
* @Route("/", name="report")
* @Method("GET")
* @Template()
*/
public function indexAction()
{
$em = $this->getDoctrine()->getManager();
$workers = $em->getRepository('NTSBSServiceBundle:Worker')->findAll();
return array(
'workers' => $workers,
);
}
I have checked, and $workers does contain entities from the database. The
twig gets rendered. If I remove the for-loop, naturally the error message
disappears.
Hoping that someone can explain to me what I'm doing wrong.