The SOAP message composer creates a DOMSource using a DOM node which has no associated Document, which causes issues with Xalan transformations in Camel. There's no requirement to use DOMSource, so change the composer to use the DOM Node as the message content instead. XmlConverter (in Camel) is available to convert a parent-less DOM Node into a proper DOMSource, so when the Camel xslt component accesses the payload with getBody(DOMSource.class), XmlConverter kicks in and creates a Document and adds the node as a child.