PushModalAsync causing an UIKit.UIView.EndEditing exception using iOS unified..

I'm getting the following exception when trying to use Navigation.PushModalAsync on iOS using the unified Xamarin.iOS dll:

System.MissingMethodException: Method not found: 'UIKit.UIView.EndEditing'.
at at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at UIKit.UIApplication.Main (System.String[] args, IntPtr principal, IntPtr delegate) [0x00005] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:62
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:46
at TestUnifiedApp.iOS.Application.Main (System.String[] args) [0x00008] in /Users/Nick/Projects/TestUnifiedApp/iOS/Main.cs:17

The "offending" code snippet is:

((Button)((Frame)((StackLayout)s.Children[2]).Children[0]).Content).Clicked += (object sender, EventArgs e) => 
{
        Navigation.PushModalAsync(new PickSlip()); //PickSlip extends from ContentPage
};

I'm using the newest updates on the Alpha channel as well as Pre-release 4 of Xamarin.Forms.