Edge release 9200 breaks app - SystemStackError

Hi,

After updaing edge rails to release 9200, I have started reciving the
following error in a new app

‘stack level too deep’

Release 9200 (titled: Add efficient #include? to AssociationCollection
(for has_many/has_many :through/habtm). [stopdropandrew]) does not seem
to have any major changes and I can’t find anything obvious that would
cause this error, does anyone have any suggestions to what may be going
wrong?

Thanks,
Scott