problema com o método getRentalServiceDocPort

["Alexandre Freire" <chegado@xxxxxxxxx>]

O código abaixo:

	public static void main(String[] args) throws Exception {
		Context initialContex = new InitialContext();
		
		VideoRentalService service = (VideoRentalService) initialContex
		.lookup("java:comp/env/service/videorental");
		
		RentalServiceRPC port = (RentalServiceRPC) service.getRentalServiceRPCPort();
	}

Funciona perfeitamente, porém quando substituo a linha

RentalServiceRPC port = (RentalServiceRPC) service.getRentalServiceRPCPort();

por

RentalServiceDoc port = (RentalServiceDoc) service.getRentalServiceDocPort();

ocorre a seguinte exception:

Exception in thread "main" javax.xml.rpc.ServiceException: Cannot create proxy
	at org.jboss.ws.jaxrpc.ServiceImpl.createProxy(ServiceImpl.java:380)
	at org.jboss.ws.jaxrpc.ServiceImpl.getPort(ServiceImpl.java:329)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.jboss.ws.jaxrpc.ServiceProxy.invoke(ServiceProxy.java:130)
	at $Proxy1.getRentalServiceDocPort(Unknown Source)
	at temp.WSClient.main(WSClient.java:21)
Caused by: org.jboss.ws.WSException: Unexpected null return parameter
	at org.jboss.ws.jaxrpc.ParameterWrapping.assertOperationMetaData(ParameterWrapping.java:71)
	at org.jboss.ws.jaxrpc.ParameterWrapping.matchRequestParameters(ParameterWrapping.java:79)
	at org.jboss.ws.metadata.OperationMetaData.getJavaMethod(OperationMetaData.java:182)
	at org.jboss.ws.metadata.EndpointMetaData.getOperation(EndpointMetaData.java:324)
	at org.jboss.ws.jaxrpc.MetaDataSynchronization.synchronizeServiceEndpointInterface(MetaDataSynchronization.java:57)
	at org.jboss.ws.jaxrpc.ServiceImpl.createProxy(ServiceImpl.java:365)
	... 8 more

Já verifiquei todos os XMLs e aparentemente estão corretos.

Obrigado.