Marco Belladelli ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=637b480... ) *commented* on HHH-16343 ( https://hibernate.atlassian.net/browse/HHH-16343?atlOrigin=eyJpIjoiN2Y2N2... ) 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=eyJpIjoiN2Y2N2... ) Hello Jones ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) and thank you for reporting the issue. The cause of the error you’re encountering is the same as we discussed in https://hibernate.atlassian.net/browse/HHH-16254 ( https://hibernate.atlassian.net/browse/HHH-16254 ) : the getEntity() method in your pre-load event is returning a proxy}}ed entity (needed for handling caching+batching associations). This, in turn, causes the {{Hibernate.getClass() method to trigger an initialization of the proxy, that leads to the pre-load event being called again with the same proxy, causing an infinite recursion loop. We’re exploring the possibility of not using a proxy in this particular case, but since it’s always possible to obtain one in a pre-load event I’d strongly suggest handling this case correctly. You could, for example, avoid forcing initialization by checking Hibernate.isInitialized( event.getEntity() ) first. ( 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 )