I'm trying to integrate lazr.restful into a Zope3 app and I was advised to created my own publication factory. For that I did <publisher name="LAZRWS" factory=".root.WSFactory" methods="GET POST HEAD DELETE" mimetypes="*" priority="5" /> Priority is set to 5 as opposed to priority 10 of the standard BROWSER declaration in zope/app/publication/configure.zcml <publisher name="BROWSER" factory=".requestpublicationfactories.BrowserFactory" methods="GET POST HEAD" mimetypes="*" priority="10" /> But although the RequestPublicationFactory class say: "The `priority` is used to define a lookup-order when multiple factories are registered for the same method and mime-type." the RequestPublicationFactory.lookup does not really take that into account. So what I did on line 104 of zope/app/publication/requestpublicationregistry.py from operator import itemgetter factory_lst = sorted(factory_lst, key=itemgetter('priority')) Now it works as expected, calling canHandle of my factory and then falling back to ".requestpublicationfactories.BrowserFactory" for non WS requests. Is this really a bug or should I be doing something different? Thanks Gustavo