AngularJS ng-class is ignored by css selectors

I'm building an ionic application and recently the dynamic class set through ng-class stopped having any effect. It is still resolved correctly in the HTML, but the selectors just don't work on it.

Here's the template:

<ion-nav-bar class="bar-positive nav-title-slide-ios7" ng-class="{{ app.style }}">
        <ion-nav-back-button class="button-clear"><i class="icon ion-chevron-left"></i> Back</ion-nav-back-button>
</ion-nav-bar>

And here's the resulting HTML, which is perfectly fine as far as I can tell:

<ion-nav-bar class="bar-positive nav-title-slide-ios7 bar bar-header nav-bar disable-user-behavior  no-animation" ng-class="Tallin">
  <ion-nav-back-button class="button-clear button back-button ng-hide"><i class="icon ion-chevron-left"></i> Back</ion-nav-back-button>
  <div class="buttons left-buttons"> <span class="">
    <button menu-toggle="left" class="button button-icon icon ion-navicon"></button>
  </span></div>
  <h1 ng-bind-html="title" class="title ng-binding" style="left: 51px; right: 51px;">Home</h1>
  <div class="buttons right-buttons"> </div>
</ion-nav-bar>

But if I now try to use .Tallin in any CSS selectors, they have no effect. I tried using it as a regular static class, just to validate the selectors, and they work.

This wasn't a problem until recently, but I'm not sure which change started it. Any ideas would be greatly appreciated.