     # Subscribe to the 'err' response for topicId
     # We don't pass a callback immediately so that we can
     # refer to the subscription itself in the callback.
-    errSub = bus.subscribe {
+    errSub = core.bus.subscribe {
       channel: channel
       topic: replyTo.topic.err
       callback: callback

        msg = "Responder with id #{responderId} timed out on channel '#{channel}'"
        err = new Error msg

        bus.publish
          channel: replyTo.channel
          topic: replyTo.topic.err
          data: err


  # just listen
  listen: (channel, topic, callback) ->
    sub = core.bus.subscribe
      channel: channel
      topic: topic
      callback: (data, envelope) ->
