To close the issue: The error in my original post is not new. See http://mail.zope.org/pipermail/zope/2004-February/146957.html and Collector issue filed on March 24: http://zope.org/Collectors/Zope/1271 This error unfortunately applies both to Zope 2.6.4 and Zope 2.7.0 -- Milos Prudek