Handlebars conditional style attribute

I am using ember 1.8.1

The controller has a property isDisplay

In handlebars, I implement like this, it works but code is too long

    <div class="form-group">
    </div>

    <div class="form-group" style="display:none;">
    </div>

I tried to using conditional, like this but it doesn't work

<div class="form-group" >
</div>