@mikethompson: Just to follow up on the above: I finally figured out the error. As you said, the subscription handler had not been registered by the time it was required. The other subscriptions in the same file were wrapped inside functions, while the troublemaker was bound to a var and hence evaluated immediately. If I could force ClojureScript to run through the subscriptions file before the other file, then I'd avoid that problem. Thanks for your patience.