Change Signature not possible for events?

v[4.5.1288.2]

The "Change signature" is disabled on the event property "Foo" below. Am I not supposed to be able  to change the signature on this via Resharper?

public interface IView
{
  //Old signature
  event Action<int> OnFoo;
  //New signature I would like to have
  //event Action<long> OnFoo;
}

Thanks.