Add WOW.js to Angular2

I install wowjs via npm:

npm install wowjs --save

Declare module on src/typings.d.ts:

declare module 'wowjs';

In app.component.ts import:

import * as WOW from 'wowjs';

And then I init wow in ngOnInit():

ngOnInit() {
  this.wow = new WOW.init();
}

Webpack: Compiled successfully. But there is an error:

via Gabriel