Oracle db query issue

In SoapUI Pro 4.5, I'm using a Groovy script to query an oracle database. The query itself is a function call which is supposed to return a CLOB of xml text. The query is of the form:

sql.eachRow("SELECT getxml(${argument1},'${argument2}')as result FROM dual") {
  payload = it.result
 }

The query returns oracle.sql.OPAQUE@c53b8c instead of the xml I'm expecting. I've tried the query in Toad so I know it works there.