OpenID delegation with application/xrds+xml stopped working

I have been doing OpenID delegation by returning https://login.launchpad.net/+id/hGyyz4f/+xrds using nginx proxy_pass from http://iny.iki.fi/ when asked for application/xrds+xml. This has worked fine for some time, but now I get:

A site identifying as http://stackoverflow.com/users/authenticate/ has asked us for confirmation that http://iny.iki.fi/ is your identity URL. However, that is not a valid Launchpad OpenID identity URL, such as https://launchpad.net/~USER