Buttons in container with data-toggle="buttons" don't get aria-pressed attribute

Toggle buttons need to have a relevant aria-pressed="true"/aria-pressed="false" attribute set to programmatically indicate their activation state. While this currently works fine for singles toggles http://v4-alpha.getbootstrap.com/components/buttons/#toggle-states, it doesn't for buttons that are inside a container with data-toggle="buttons" ... here, active gets correctly set/unset, but no aria-pressed attribute is added/updated accordingly.

<div class="btn-group" data-toggle="buttons">
<button class="btn btn-secondary" type="button">One</button> 
<button class="btn btn-secondary" type="button">Two</button>
</div>

Test case: https://jsfiddle.net/11o6oxcg/2/