Node of this type cannot be added

Hello
I get the following stack when I try to process an XSQL page with a serializer attribute in the xml-stylesheet tag. The FOP is fop 0.20.5:

Oracle XDK Java 9.2.0.5.0 Production
XSQL-018: Unexpected Error Occurred processing stylesheet stylesheet/rptAccess.xsl
oracle.xml.parser.v2.XMLDOMException: Node of this type cannot be added.
at oracle.xml.parser.v2.XMLDocument.checkChildType(XMLDocument.java:443)
at oracle.xml.parser.v2.XMLNSNode.checkNodePermissions(XMLNSNode.java:562)
at oracle.xml.parser.v2.XMLNSNode.appendChild(XMLNSNode.java:382)
at oracle.xml.parser.v2.XMLDocument.appendChild(XMLDocument.java:485)
at oracle.xml.parser.v2.XMLNSNode.appendChild(XMLNSNode.java:374)
at oracle.xml.parser.v2.XMLDocument.appendChild(XMLDocument.java:485)
at oracle.xml.xsql.XSQLStylesheetProcessor.processToDocument(XSQLStylesheetProcessor.java:69)
at oracle.xml.xsql.XSQLPageProcessor.process(XSQLPageProcessor.java:277)
at oracle.xml.xsql.XSQLServlet.doGet(XSQLServlet.java:60)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
...
at java.lang.Thread.run(Thread.java:536)

Has anyone run into this problem before? Or does someone have a clue on how this can be solved. Is it a problem with the xml parser? The stylesheet work fine when used with an xml document.

 

Would appreciate some response asap!

 

Thanks,

Francine.