Comment 1 for bug 1525884

lahari: Hi. could you provide more information:
 - which version of Heat do you use?
 - could you show share your template?
 - which commands you exactly executed?

I tried something similar on your scenario:

- create stack with template, which has one parameter (without default value)
- then update it in way, that it fails
- execute stack-list - it works for me.

http://paste.openstack.org/show/481810/