kUTTypeURL undefined — Use of unresolved identifier 'kUTTypeURL' in Swift

I'm having trouble getting a sharing extension to work. I have the following in my sharing controller. ``` let item: NSExtensionItem = self.extensionContext.inputItems[0] as NSExtensionItem let itemProvider: NSItemProvider = item.attachments[0] as NSItemProvider var URL: NSString if itemProvider.hasItemConformingToTypeIdentifier(kUTTypeURL) { itemProvider.loadItemForTypeIdentifier(kUTTypeURL, options: nil, completionHandler: {(url: NSURL, error: NSError) in URL = url.absoluteString }) } self.extensionContext.completeRequestReturningItems(nil, completionHandler: nil) ``` This gives me the error `Use of unresolved identifier 'kUTTypeURL'` on the line `if itemProvider.hasItemConformingToTypeIdentifier(kUTTypeURL) {`. It seems to be defined as a constant in Swift, but I can't seem to access it. Is it part of an enum? Do I have to import something to get access to it? Thanks for your help.