Here's my simple TODO app with basic error handling using your handle_errors decorator: https://gist.github.com/SamuelMarks/9d7c796b8a336bb556f3 Unfortunately it is always throwing 500s. Is there some other way I'm meant to be passing errors? E.g.: in Node.js most of my functions have the signature (err, res). Thanks for all assistance PS: The functions from line 103 to 110 was another attempt of mine to get exceptions handled PPS: Issue reported 10 days ago - https://github.com/twisted/klein/issues/58