How to respond to caller in kroma.runtime/on-message

I’m writing chrome extension with kroma.

I’m calling following function in my popup.cljs:

(defn my-caller-function [timer]
  (runtime/send-message {:foo :bar
                         :responseCallback do-something}))

I’m listening to messages in my background.cljs

(defn init []
    (when-let [message (

As far as I understand do-something should be called with "foo" as argument. But it isn't.

What am I doing wrong?