   ///
   /// - parameter queue: the dispatch queue upon the new `Deferred`'s notifications will be performed
 
-  public func deferred(queue: DispatchQueue) -> Deferred<Wrapped>
+  public func deferred(queue: DispatchQueue) -> Deferred<Wrapped, Invalidation>
   {
     switch self
     {

  ///
  /// - parameter qos: the QoS at which to perform notifications for the new `Deferred`; defaults to the current QoS class.

  public func deferred(qos: DispatchQoS = .current) -> Deferred<Wrapped>
  {
    let queue = DispatchQueue(label: "deferred", qos: qos)
    return self.deferred(queue: queue)

  /// - parameter value: the value to be validated

  public func validate(qos: DispatchQoS,
                       predicate: @escaping (_ value: Success) -> Bool, message: String = "") -> Deferred<Success, Error>
  {
    let queue = DispatchQueue(label: "deferred", qos: qos)
    return validate(queue: queue, predicate: predicate, message: message)
