         let operation = ResourceListOperation(configuration: configuration, queue: self.streamQueue)
         operation.completionBlock = {
             [weak operation] in
-            let strongOperation = operation!
-            self.completionHandlerQueue.addOperationWithBlock {
-                completionHandler(strongOperation.resources, strongOperation.error)
+            if let strongOperation = operation {
+                self.completionHandlerQueue.addOperationWithBlock {
+                    completionHandler(strongOperation.resources, strongOperation.error)
+                }
             }
         }
         operation.path = path

        let operation = FileDownloadOperation(configuration: configuration, queue: self.streamQueue)
        operation.completionBlock = {
            [weak operation] in
            let strongOperation = operation!
            self.completionHandlerQueue.addOperationWithBlock {
                completionHandler(strongOperation.fileURL, strongOperation.error)
            }
        }
        operation.path = path

        let operation = DirectoryCreationOperation(configuration: configuration, queue: self.streamQueue)
        operation.completionBlock = {
            [weak operation] in
            if let strongOperation = operation {
                self.completionHandlerQueue.addOperationWithBlock {
                    completionHandler(strongOperation.error == nil, strongOperation.error)
                }
            }
        }
        operation.path = path
