Using multibytes characters in bpmn2 makes an svg which contains Invalid byte character

When bpmn2 file contains multi-byte characters,
the characters within svg made from the bpmn2 cannot be displayed with UTF8.

In Addtion to that ,
This Error occures in runtime,
process instance diagram isn't displayed.

Caused by: org.apache.batik.dom.util.SAXIOException: Invalid byte 1 of 1-byte UTF-8 sequence.
at org.apache.batik.dom.util.SAXDocumentFactory.createDocument(SAXDocumentFactory.java:459)
at org.apache.batik.dom.util.SAXDocumentFactory.createDocument(SAXDocumentFactory.java:357)
at org.apache.batik.anim.dom.SAXSVGDocumentFactory.createDocument(SAXSVGDocumentFactory.java:225)
at org.jbpm.process.svg.SVGImageProcessor.<init>(SVGImageProcessor.java:44)
... 59 more
Caused by: org.xml.sax.SAXParseException; systemId: http://jbpm.org; lineNumber: 1; columnNumber: 27231; Invalid byte 1 of 1-byte UTF-8 sequence.
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:201)