The type `MonoTouch.UIKit.UIViewController' is defined Error when I convert to Unified API

I have created a new Xamarin.Forms.Portable project.
After that I wanted to convert MYProjectName.IOS to Unified by going to Project > Migrate to Xamarin Unified API

So I did that and removed all MonoTouch name references.
Next, when I try to compile this project I am getting this error message.

Can you please help. Error is on this line of code:

window.RootViewController = App.GetMainPage().CreateViewController();

Error Message:
The type MonoTouch.UIKit.UIViewController' is defined in an assembly that is not referenced. Consider adding a reference to assemblymonotouch, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065' (CS0012)

Thank You