     }
     
     /// Dispatch queue that queues up and dispatches handler blocks
-    private let handlerQueue: dispatch_queue_t
+    private let handlerQueue: NSOperationQueue
     
     /// Session data task that refers the lifetime of the request.
     private var dataTask: NSURLSessionDataTask?

     - returns: Self instance to support chaining.
    */
    public func response(handler: ResponseProcessingHandler) -> Self {
        dispatch_async(handlerQueue) {
            if let taskResult = self.taskResult {
                switch taskResult {
                case .Failure(_): return // bail out to avoid next handler from running

            taskResult = ServiceTaskResult.Failure(error)
        }
        
        handlerQueue.suspended = false
    }
}

