Popover wrapped into btn-group is blank

Created by: aldesantis

<div class="btn-group">
    <a class="btn" rel="popover" data-content="Lorem ipsum dolor sit amet.">Click me!</a>
</div>

Clicking the button results in a blank popover appearing. Am I doing something wrong or is this an issue? If so, is there any workaround in the meantime?

Thanks in advance.