AngularJS: dynamically assign controller from ng-repeat

I'm trying to dynamically assign a controller for included template like so:

<section ng-repeat="panel in panels">
    <div ng-include="'path/to/file.html'" ng-controller="{{panel}}"></div>
</section>

But Angular complains that {{panel}} is undefined.

I'm guessing that {{panel}} isn't defined yet (because I can echo out {{panel}} inside the template).

I've seen plenty of examples of people setting ng-controller equal to a variable like so: ng-controller="template.ctrlr". But, without creating a duplicate concurrant loop, I can't figure out how to have the value of {{panel}} available when ng-controller needs it.

P.S. I also tried setting ng-controller="{{panel}}" in my template (thinking it must have resolved by then), but no dice.