Dimmer's closable setting not working

Here is the jsfiddle code

why the dimmer is still closable when initialized with closable=false?

$('.dimmer').dimmer({closable:false, on:'click'})

HTML

<div class="ui container">
  <div class="ui segment dimmerable">
    <div class="ui dimmer">
      <div class="ui content">
        <div class="ui inverted center header">
          Dimmer
        </div>
      </div>
    </div>
    Segment
  </div>
</div>