The extension needs to be disabled and enabled again in about:addons. Then it starts working again. I have observed the same behaviour when using the chrome namespace instead of the browser namespace in background.js. +++ This bug was initially created as a clone of Bug #1197422 +++ https://developer.chrome.com/extensions/pageAction API is listed on https://wiki.mozilla.org/WebExtensions#List_of_APIs_we_will_likely_support_in_the_future

Works for me. Do you have a testcase?

I am just using you test-panel.xpi from Bug #1197422. It works after I install it in nightly Firefox, on the Windows XP machine with latest nightly. Then I File->Quit Firefox and start it again. Now the PageAction icon does not show. The Browser Action icon is there. After I disable and enable the add-on in about:addons the pageAction icon becomes visible again. I did switch tabs to make sure the listener should get triggered, but it only works after disable/enable after a browser restart.

I think that just has something to do with the way the add-on is implemented, and the order that the listeners are dispatched. I have other test add-ons that work as expected after a restart.

Since this seems to have been fixed, I'm removing dev-doc-needed.

I think that was just there because this bug was cloned from a bug that actually needed it.