An item with the same key has already been added.

VS2013 Beta channel xamarin.ios
On nugget update of Xamarin.Forms I get
"An item with the same key has already been added."

Installing 'Xamarin.Forms 1.2.3.6257'.
Successfully installed 'Xamarin.Forms 1.2.3.6257'.
Updating 'Xamarin.Forms' to version '1.2.3.6257' in project 'App1'.
Removing 'Xamarin.Forms 1.0.6186' from App1.
Successfully removed 'Xamarin.Forms 1.0.6186' from App1.
Adding 'Xamarin.Forms 1.2.3.6257' to App1.
Uninstalling 'Xamarin.Forms 1.2.3.6257'.
Successfully uninstalled 'Xamarin.Forms 1.2.3.6257'.
Install failed. Rolling back...
An item with the same key has already been added.