SQL Stored Procedure - Function sequence error

I have a service program that has a procedure that returns a result set (not a return value). I have a stored procedure created over it.

However when I call it from Java, I get "Function sequence error."

From the service program procedure

26636P GetVertexGeoCodeList...
26636P B Export
26636D PI
26636D epZip4 9a Const

26636D ds_GeoCode DS Occurs( 6 )
26636D GeoCode 9a

26636 EXEC SQL
26636 SET RESULT SETS FOR RETURN TO CLIENT ARRAY :ds_GeoCode FOR :i ROWS;



Stored Procedure:

CREATE PROCEDURE CCDLIB/GETVERTEXGEOCODELIST
(IN EPZIP4 CHAR (9 ))
LANGUAGE RPGLE
NOT DETERMINISTIC
READS SQL DATA
EXTERNAL NAME CCDLIB/VERTEXS(GETVERTEXGEOCODELIST)
PARAMETER STYLE GENERAL


Java call:
ResultSet selectRS = stmt.executeQuery("CALL CCDLIB.GETVERTEXGEOCODELIST('537040000')");


Any idea what I'm doing wrong?

On IBM i 7.1

Thanks,
Kurt
Ps. I've had success creating stored procedures over programs. This is my first attempt over a service program procedure.