             func URLSession(session: NSURLSession!, dataTask: NSURLSessionDataTask!, didReceiveResponse response: NSURLResponse!, completionHandler: ((NSURLSessionResponseDisposition) -> Void)!) {
                 var disposition: NSURLSessionResponseDisposition = .Allow
 
-                if self.dataTaskDidReceiveResponse {
+                if self.dataTaskDidReceiveResponse != nil {
                     disposition = self.dataTaskDidReceiveResponse!(session, dataTask, response)
                 }
 

        }

        let request = Alamofire.Request(session: self.session, task: uploadTask)
        if stream {
            request.delegate.taskNeedNewBodyStream = { _, _ in
                return stream
            }

    class func propertyListResponseSerializer(options: NSPropertyListReadOptions = 0) -> (NSURLRequest, NSHTTPURLResponse?, NSData?, NSError?) -> (AnyObject?, NSError?) {
        return { (request, response, data, error) in
            var propertyListSerializationError: NSError?
            let plist: AnyObject! = NSPropertyListSerialization.propertyListWithData(data, options: options, format: nil, error: &propertyListSerializationError)

            return (plist, propertyListSerializationError)
        }
