Unable to invoke an EJB deployed on JBoss 7.1 from JBoss ESB 4.10

Question

I'm trying to invoke an Stateless Session Bean (EJB 3) deployed on Jboss 7.1 Final from an remote instance of JBoss ESB 4.10. In my jboss-esb.xml I have the following information:

<action name="EJBTestWithReturnValue" class="org.jboss.soa.esb.actions.EJBProcessor">
    <property name="ejb3" value="true" />
    <property name="method" value="login" />
    <property name="jndi-name" value="gwtbatis-ear/gwtibatis-ejb/UserServiceEJB!com.aestasit.gwtibatis.UserServiceRemote" />
    <property name="initial-context-factory" value="org.jnp.interfaces.NamingContextFactory" />
    <property name="security-principal" value="xxxx" />
    <property name="security-credentials" value="xxxx" />
    <property name="provider-url" value="localhost:4447" />
    <property name="ejb-params">
        <arg0 type="java.lang.String">username</arg0>
        <arg1 type="java.lang.String">password</arg1>
    </property>
    <property name="esb-out-var" value="org.jboss.soa.esb.message.defaultEntry"/>

Whatever JNDI binding I try I always get an error "invalid stream header: 00000018". I successfully invoke the same EJB from a Java client but I use a different context factory ("org.jboss.naming.remote.client.InitialContextFactor").

Is there a way to invoke the remote EJB from ESB, without importing the client lib required by JBoss 7 and wriying my own EJB invoker?