Can't get ViewCild to work on JS

I’ve updated Ionic from beta.6 to beta.9 but I can’t get the View Child to work…

How my app works:
app.js has the main nav: <ion-nav #myNav [root]="rootPage"></ion-nav>
In app.js I set the rootPage LoginPage. When logged in the NavController sets the root TabsPage.
Now I want to log out and set the rootpage LoginPage. This worked with the app.getComponent but with the View child not…

Error: Cannot read property ‘setRoot’ of undefined

So app.js:
<ion-nav #myNav [root]="rootPage"></ion-nav>


import {ViewChild} from '@angular/core'; <-----
//more imports

    templateUrl: 'build/tab_Settings/Settings/SettingsPage.html',
    queries: {
        rootNav: new ViewChild('myNav')   <-------
export class SettingsPage{    
    //basic class stuff

        this.rootNav.setRoot(LoginPage); <------

Thanks in advance!