SSIS Job Failure @P21 error

My SSIS job fails with an @P21 error message

Huh?  There is no such parameter in my stored procedure.  There are quite a few, but not 21 of the dratted things. 

The job was trying to run a stored procedure to updated changed records.  The procedure ran perfectly well in SQL server.  But not when I built it into an SSIS job.

Here's why.  Muggins here typed:
exec usp_update ?.?.?.?.?

And I should have written:
exec usp_update ?,?,?,?,?

D'oh!