I believe the function signature of localized will need to match the function signature of NSLocalizedString for genstrings to pick up the strings from code.  I have re-made my function: localized(_ key: String, tableName: String? = nil, bundle: Bundle = Bundle.main, value: String = "", comment: String = "") - String Still getting the same errors :( Our recommendation is that you should always include in a comment to localizers for context; hence why this property is required for NSLocalizedString in Swift. Thanks for the advice, but it's a deliberate decision. I am a localizer for the app. Instead of the func, you could define String extension, with a property or a func I thought about it, but writing "bla-bla-bla".localized looks ugly for my taste.