Add a Boundary Event to a Task

If I have a boundaryEvent in a Task (which should be legal for BPMN2), I have this exception when I add the definition to the knowledge base:

java.lang.ClassCastException: org.jbpm.workflow.core.node.WorkItemNode cannot be cast to org.jbpm.workflow.core.node.CompositeContextNode
at org.jbpm.bpmn2.xml.ProcessHandler.linkBoundaryEvents(ProcessHandler.java:265)
at org.jbpm.bpmn2.xml.ProcessHandler.end(ProcessHandler.java:130)
at org.drools.xml.ExtensibleXmlParser.endElement(ExtensibleXmlParser.java:414)
at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
at org.apache.xerces.impl.xs.XMLSchemaValidator.endElement(Unknown Source)
at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanEndElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl.parse(Unknown Source)
at org.drools.xml.ExtensibleXmlParser.read(ExtensibleXmlParser.java:293)
at org.drools.xml.ExtensibleXmlParser.read(ExtensibleXmlParser.java:172)
at org.jbpm.compiler.xml.XmlProcessReader.read(XmlProcessReader.java:46)
at org.jbpm.compiler.ProcessBuilderImpl.addProcessFromXml(ProcessBuilderImpl.java:249)
at org.drools.compiler.PackageBuilder.addProcessFromXml(PackageBuilder.java:516)
at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:560)
at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:28)