Jones ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *commented* on HHH-16343 ( https://hibernate.atlassian.net/browse/HHH-16343?atlOrigin=eyJpIjoiNjE5ND... ) Re: Batch Fetch Size + PreLoadEventListener + Polymorphic Entity with cache enabled could lead to IllegalStateException: Illegal pop() with non-matching JdbcValuesSourceProcessingState ( https://hibernate.atlassian.net/browse/HHH-16343?atlOrigin=eyJpIjoiNjE5ND... ) Ok, thanks. On hibernate 5 the PreLoadEvent always had the Object[] state and that's why I was using it. Switching to PostLoadEvent , I can obtain the Object[] state using event.getPersister().getValues(event.getEntity()) and I assume the PostLoadEvent will never have an uninitialized proxy. ( https://hibernate.atlassian.net/browse/HHH-16343#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16343#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100219- sha1:ac3e918 )