[plt-scheme] SrPersist Question on NULLS

I have a SQL statement that includes a column pkpos. It is an Integer, or else NULL. I cannot see in
the docs how to bind this result - it gives an error with NULL values.

The pertinant code is:

(define pkpos-buffer (make-buffer 'sql-c-slong))

(define pkpos-buffer (make-buffer 'sql-c-slong))

(bind-col hstmt 6 pkpos-buffer pkpos-indicator)

"Unspecified error in fetch"

Alex