How can i insert a 1024x1024 marketing icon in my iOS app appicons catalog

I am using Xamarin Studio on a MAC, and using the asset catalog for my appicons. I cannot successfully upload the app to the store as the 1024x1024 app icon is missing.
When I open the appicons view from the Media.xcassets tab, there is no entry for the 1024x1024 icon.
(In VS2015 there is an entry for it, but none of the icons added in VS2015 appear when you open the project on the mac).