Encoding issue with groovy.xml.XmlUtil.serialize()

http://groovy.329449.n5.nabble.com/Encoding-issue-with-groovy-xml-XmlUtil-serialize-td5038513.html

I think it should be possible to put an 'ü' charter in the xml element.

def xml ="""<?xml version="1.0" encoding="UTF-8"?>
<Schlüssel>
text content
</Schlüssel>"""

groovy.util.slurpersupport.GPathResult s = new XmlSlurper().parseText(xml)

println groovy.xml.XmlUtil.serialize(s) // results in empty xml, why?

----- OUTPUT
<?xml version="1.0" encoding="UTF-8"?>

WORKAROUND
def outxml = new groovy.xml.StreamingMarkupBuilder().with

println outxml