Invoking stored procedures through the SQL plugin

I'm currently trying to use stored procedures as part of a workflow to enrich a database.

I've had partial success using the example code from Call Database Stored Procedures via JDBC, however the JDBC driver seems to choke when I try to feed an Integer parameter.

For example:

var mask=24;

cstmt.setInt(2, mask);

results in a

InternalError: java.lang.NullPointerException (Workflow:Start Session / Scriptable task (item2)#260(eval)#1)

possibly a unique problem (not many people invoking stored procs from vCO I suspect) but maybe the developers have an idea?