serviceTask with no interfaces are not supported

With JBPM 5.1, if I define a Service Task with no interfaces for instance using the new BPMN2 eclipse editor this is not accepted.
Indeed, when I load the resource in the knowledge base, I see:
java.lang.IllegalArgumentException: No interfaces found
at org.jbpm.bpmn2.xml.ServiceTaskHandler.handleNode(ServiceTaskHandler.java:51)
at org.jbpm.bpmn2.xml.TaskHandler.end(TaskHandler.java:188)
at org.drools.xml.ExtensibleXmlParser.endElement(ExtensibleXmlParser.java:414)

A serviceTask with no interfaces should be legal in BPMN2:see table 10.46, pag 201 in the specs (http://www.omg.org/spec/BPMN/2.0/) for the serviceTask schema.
That affects both the runtime and the "old" flow designer.