AirCheap: problem with flux/utils MapStore extending?

[allizad]

Working through the Aircheap example and keep hitting this wall:

RouteStore.js?1441:3

Uncaught TypeError: Super expression must either be null or a function, not undefined
    

I've gotten to the point of just copying over the code exactly from here, and still having this issue. Any clue? Tried using RouteStore extends FluxStore.MapStore, but still got the same problem. Am I missing something?

Thanks in advance.