pg_dump warning message

Postgres version: 7.3.4
Environment: Solaris (SunOS 5.9) Ultra-250
We use pg_dump to do a nightly export of all databases, via these commands:

for instance in $(get_instances) ; do
  outfile=${exportdir}/${instance}~EXPORT~${ymd}.sql
  su - ${pg_user} -c "${pg_home}/bin/pg_dump -c -C -D -F c -f ${outfile} ${instance}"
  gzip ${outfile}
done

The pg_dump switches indicate a "custom" file format, and the output file is a standard plain-text UNIX file.
Nevertheless, when the export runs, it throws this warning for each database instance:

pg_dump: [archiver] WARNING: requested compression not available in this installation - archive will be uncompressed

This does not appear to affect the contents of the export file--but it would be nice to understand what is generating these messages--and to eliminate the chatter (which the system crontab treats as error messages);

--

David Rickard
Software Engineer
The GTS Companies
A TechBooks Company

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