messageExchange.responseContent is always null on REST Request test step

Hi forum

I want to to add a script assertion to a REST Request test step to be able to do an xml schema validation. First of all I need access to the response object, ie:

def holder = groovyUtils.getXmlHolder( messageExchange.responseContent )

My problem is that no matter what I do the messageExchange.responseContent object is always null. Am I missing something obvious?

Regards,

Rune