unable to click on button inside "input-group-btn"

[jelkevdh]

If I have a button like this:

            <div class="form-group">
                <div class="col-sm-10">
                    <div class="input-group">
                        <span class="input-group-btn">
                            <button type="button" id="selectType" class="btn btn-primary" ng-click="selectType()" translate="SELECT"></button>
                        </span>
                    </div>
                </div>

Then the curtain prevents me from clicking it. Have been playing with it for quite some time, but cannot figure out why that is.
(In the example I left out some irrelevant HTML)