         url defaultURL: NSURL? = nil
         ) {
             self.cacheFile = cacheFile
-            errorCompletion = nil
-            completion = nil
+            _error         = nil
+            _completion    = nil
             
             super.init(operations: [])
             name = "DownloadJSONOperation<\(self.dynamicType)>"

                let json = try NSJSONSerialization.JSONObjectWithData(data,
                    options: .MutableContainers
                    ) as? [String:AnyObject]
                completion?(json)
            } catch let error as NSError {
                errorCompletion?(error)
                finishWithError(error)
                
                return

        error: (NSError -> Void)?
        ) {
            cacheFile = NSURL()
            _error = error
            _completion = completion
            
            super.init(operations: [])
            name = "DownloadJSONOperation<\(self.dynamicType)>"
