The exception occurs on entityManagerFactory.getPersistenceUnitUtil().getIdentifier(entity), passing a detached and enhanced entity as argument. When I disable hibernate-enhance-maven-plugin or back to 5.2.2, the exception don't happens.

Stack Trace:

Exception in thread "pool-1-thread-1" java.lang.NullPointerException
at org.hibernate.jpa.internal.PersistenceUnitUtilImpl.getIdentifier(PersistenceUnitUtilImpl.java:74)
at br.com.flextotal.ServerInitListener.serverInit(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

I created a test case in this fork: https://github.com/edallagnol/hibernate-test-case-templates/tree/master/orm/hibernate-orm-5/src/