ember: Ember 2.4 change main view css class

I'm looking for a way to change the css classname of the root element of an Ember app in Ember 2.4.

The old way doesn't work anymore because of deprecation, and now I have :

<body class="ember-application">
   <div id="ember414" class="ember-view">
     <!-- THE WHOLE APP -->
   </div>
</body>

I'm looking for making something like :

<body class="ember-application">
   <div id="ember414" class="ember-view theCssClass">
     <!-- THE WHOLE APP -->
   </div>
</body>

Thanks a lot for your help !

ember