If you use the 'find' option in the change sorter and accept nothing, you will get a notifier since #classNotFound is sent and not understood. It actually looks more like a logic snafu, since I suspect it would be more useful simply to return after an empty input. The 'classNotFound' is probably more useful after a pattern is accepted and nothing matches. Whoever wrote the method (system claims dan did) might like to check and see if a wrong version got released.