Forms project iOS with VS 2013 Method not found: 'Xamarin.Forms.BindableObjectExtensions.SetBinding

Hi,

I have a Forms project with a iOS native app which runs perfectly with XamarinStudio on the Mac.
If I copy the project to Windows/Visual Studio 2013 SP2 and start the iOS project I get this error:

--> System.MissingMethodException: Method not found: 'Xamarin.Forms.BindableObjectExtensions.SetBinding'.

I am using MVVM with binding, no XAML.

No change to debug.

This is the code where the exception occurs:

public static class App
    {
        public static Page GetMainPage()
        {                      
            var employeeViewModel = new EmployeeViewModel();

            var mainNav = new NavigationPage(new StartPage(employeeViewModel)); // here the exception pops up
            return mainNav;
        }
    }

Any ideas ?

Best

Marco