It looks like this was fixed in #32, but the debugger was never fixed. Specifically it's complaining about this line https://github.com/pushtell/react-ab-test/blob/master/lib/debugger.js#L97 ie. https://github.com/pushtell/react-ab-test/blob/master/src/debugger.jsx#L81