I think that it's because this overload uses magic™ to deduce the view property to be bound. Hence there is no static type deduction for the view-prop. I don't see any easy way out (except maybe remove the overload? I am not too convinced by the value of magic bindings), or you can create a non-generic interface `IReactiveBinding`, or  you could create a generic covariant interface for one way bindings (I think that one way bindings are covariant in the view property, as its essentially a `IObservable<TViewProp>`. Two-way bindings are definitely invariant though), and return an instance with static type of with `TViewProp` onto `object`.