Data binding selected broken

With the Polymer 2.0-preview, I have

`<iron-swipeable-pages selected="{{selectedIndex}}">` attached to
```
selectedIndex: {
    type: Number,
    value: 0,
    observer: '_indexChanged'
}
```

In my function I check if the value is equal to 2 and then I set `this.selectedIndex = 1` and this deselects everything and hides all the pages. Anyone know of a solution?