Validate xml against DTD

Hi guys,

Could you please advise how is possible to validate xml-response invoked from JMS queue against DTD-schema file.

I use Script assertion:

def Xmlresponse = messageExchange.getResponseContentAsXml()
def validating = true        // default is false
def namespaceAware = false   // default is true
assert new XmlParser(validating, namespaceAware).parseText(Xmlresponse)

I always get 'passed' even if DTD file is wrong.