casting to integer in geojson

Is there any reason that FME would not cast a value to an integer using xs:int(value)?

i keep getting:

"xs:string": invalid value for cast/constructor: can not cast to "xs:int"

the incoming value is a 12 digit number from a GML file with type: xml_int64

i try it without the cast and the JSONTemplator works but it comes out as a string when i need it as an integer.