You could leave the `.badge` class and just change the `badge-*` class to `label-*`. This would apply the colors while keeping the badge look. Something like this would work:

    %span.badge{class: issue.closed? ? 'label-danger' : 'label-info'} ##{issue.iid}

If you look at the [Bootstrap CSS](https://github.com/twbs/bootstrap/blob/master/dist/css/bootstrap.css#L4290-L4331), you can see that the `label-*` class does not actually need to be associated with the `label` class.