In Zope 2.7.5-final, python 2.3.5, freebsd6 with Transient Object Container settings: Data timeout: 20 Timeout resolution: 20 Maximum subobjects: 1000 and a python script that does this: req = context.REQUEST prev_order=(req.SESSION.get('order')) if prev_order == None: order=[] else: order = prev_order order.append(req.form) req.SESSION.set('order',order) my data ends up looking like this: order [{}, {}, {'foo': '1', 'bar': 'a'}, {}, {'foo': '2', 'bar': 'b'}, {'foo': '6', 'bar': 'z'}, {'foo': '1', 'bar': 'a'}] I've seen http://mail.zope.org/pipermail/zope-dev/2006-July/027890.html and am aware that related bug existed prior to 2.7.1. I've used sessions without problems before, this is the first time I attempt to store variables in containers. What am I doing wrong? Norbert