Thanks - that worked!

Do you know why that's necessary and why it wasn't mentioned in the tutorial?

You probably need to install a more recent version of Node.js. That's one of the first things mentioned.

Thanks, David. Upgrading to Node 7.4.0 allowed me to run `node main.js` without having to pass the flag.

Granted, I was using an outdated version of Node, but perhaps it'd be helpful to add a >= version number to the Node dependency blurb (a la JDK 8).

Either way, thanks for your continued efforts!

One more thing: the `repl/repl*` function call's map argument is missing a closing `}`.