Is showWhen broken?

I don't know why showWhen="ios" and showWhen="android" is always evaluated to false although there is class="ios" in the html body.

HTML

<ion-buttons start>
  <button (click)="dismissLoginModal()">
    <span primary showWhen="ios">Cancel</span>
    <ion-icon name="close" showWhen="android"></ion-icon>
  </button>
</ion-buttons>

DOM

<ion-buttons start>
    <button class="bar-button bar-button-default bar-button-icon-right">
      <span primary showwhen="ios" hidden>Cancel</span>
      <ion-icon name="close" role="img" showwhen="android" class="ion-ios-close" aria-label="close" hidden></ion-icon>
    </button>
</ion-buttons>