Hmm, my mistake, looks like a simple bug trying to access all of the values in the Map. One of the values happens to be the org.jboss.weld.util.ForwardingBeanManager which delegates to the CDI BeanManager later. I think that Binder.bindIdentifierGenerator() should use containsKey().

Caused by: java.lang.NullPointerException
at org.jboss.weld.util.ForwardingBeanManager.equals(ForwardingBeanManager.java:250)
at java.util.Hashtable.contains(Hashtable.java:371) [rt.jar:1.7.0_51]
at org.hibernate.metamodel.internal.binder.Binder.bindIdentifierGenerator(Binder.java:1327)