Ejb3DescriptorHandler which creating containers out of metadata, incorrectly creates a StatefulContainer if the metadata is of type session and not a stateless bean:

if (enterpriseBean.isSession())

{ if (((JBossSessionBeanMetaData) enterpriseBean).isStateless()) return EJB_TYPE.STATELESS; else return EJB_TYPE.STATEFUL; }

This no longer is a valid assumption because of the new Singleton bean in EJB3.1. As a result, this piece of code incorrectly ends up creating a stateful container for a singleton bean.