Delegate method for handling change in shipping method not being called

I have set up, a view controller as PKPaymentAuthorizationViewControllerDelegate.


paymentAuthorizationViewController:didAuthorizePayment:completion and paymentAuthorizationViewControllerDidFinish: are being called at appropriate times. I have shipping methods set on the payment request. I see them in the apple payment form and can switch between them. I have also implemented paymentAuthorizationController:didSelectShippingMethod:handler which is another method on PKPaymentAuthorizationViewControllerDelegate. But when I switch between shipping methods, it's never being called.