Adding new PCL into Xamarin.Forms project

I've created Xamarin.Forms project. Four projects: PCL + iOS, WP and Android:
- TestApp.Mobile
- TestApp.Mobile.iOS
- TestApp.Mobile.WinPhone
- TestApp.Mobile.Droid

I want to keep my viewmodels in another PCL, so I created PCL - TestApp.ViewModels (same dependencies as TestApp.Mobile) and added it as a reference to TestApp.Mobile PCL. It all compiles.

And here is my problem: It only works on Windows Phone. It doens't work on iOS and Android. During runtime it cannot load PCL with viewmodels (TestApp.ViewModels). The exceptions thrown is:

System.IO.FileNotFoundException: Could not load file or assembly 'CrossHello.ViewModels' or one of its dependencies