possible bug seen with -DCLOBBER_CACHE_ALWAYS and changing GUCs

SQL:

set datestyle to postgres,us;
prepare stmt as select '02-01-2011'::date::text;
execute stmt;
set datestyle to postgres,euro;
execute stmt;
deallocate stmt;

The results I get with normal debug compilation are:

SET
PREPARE
    text
------------
 02-01-2011
(1 row)

SET
    text
------------
 01-02-2011
(1 row)

DEALLOCATE

But with -DCLOBBER_CACHE_ALWAYS and -DRELCACHE_FORCE_RELEASE, I get:

SET
PREPARE
     text
------------
 02-01-2011
(1 row)

SET
    text
------------
 02-01-2011
(1 row)

DEALLOCATE

Which one of those results is correct?

Regards,
Jeff Davis