CMT JTA, but "no transaction is in progress"

I'm able to call entityManager.merge(obj), but not entityManager.flush().

I am getting "no transaction in progress".

My application context has:

<jee:jndi-lookup jndi-name="${persistenceEMFJndiServerName}"
    id="entityManagerFactory" expected-type="javax.persistence.EntityManagerFactory" />


<bean id="entityManager"
    class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager" >
</bean>

My persistence unit says transaction-type="JTA"

and I'm loading it via

@PersistenceContext 
private EntityManager entityManager;

I've tried a few things, like entityManager.joinTransaction(), entityManager.getTransaction().begin()/.end(), @Resource UserTransaction with BEAN transaction management, but it says I cant, with JTA. There's just no transaction going on.

My method has

@Transactional  
@TransactionAttribute(TransactionAttributeType.REQUIRED)  

and it's an EJB, so I'm getting pretty annoyed. CMT JTA is supposed to do transactions all by itself.