Unable To Convert From org.mozilla.javascript.UniqueTag to INFOTABLE

Hello,

I'm trying, from a service, to run this code:

var params = {
 containerUfid: undefined /* STRING */,
 criteria: "name=32344444" /* STRING */,
 type: "wt.part.WTPart" /* STRING */,
 dataShape: demo.wt.part.WTPart" /* DATASHAPENAME */
};
// result: INFOTABLE
var Result = Things["ptc-windchill-demo-thing"].Query(params);

The error message I receive is: "Unable To Convert From org.mozilla.javascript.UniqueTag to INFOTABLE".

I defined as service's output

base type: INFOTABLE

data shape: demo.wt.part.WTPart

What am I doing wrong ?

Thanks