This issue is created automatically through a Github pull request on behalf of raziel057:
It seems there is a regression since the commit https://github.com/doctrine/doctrine2/commit/53a5a48aed7d87aa1533c0bcbd72e41b686527d8#commitcomment-5696972
Doctrine\ORM\PersistentCollection can be populated in $changeSet if you set a PreUpdate and PostUpdate event. It was not the case before.
Original issue: http://www.doctrine-project.org/jira/browse/DDC-3033