BUG #12779: pg_dump -Fd doesn't care about -Z

The following bug has been logged on the website:

Bug reference: 12779
Logged by: Christoph Berg
Email address: christoph(dot)berg(at)credativ(dot)de
PostgreSQL version: 9.4.1
Operating system: Linux (Debian 8)
Description:

pg_dump -Fd doesn't seem to care about -Z for Z > 0:

$ for i in {0..9}; do echo $i; pg_dump -Z$i -Fd -f $i.fd postgres ; done
$ du ?.fd
5392 0.fd
1164 1.fd
1164 2.fd
1164 3.fd
1164 4.fd
1164 5.fd
1164 6.fd
1164 7.fd
1164 8.fd
1164 9.fd

In contrast with -Fc, where it works:

$ for i in {0..9}; do echo $i; pg_dump -Z$i -Fc -f $i.fc postgres ; done
$ du ?.fc
7548 0.fc
1488 1.fc
1440 2.fc
1392 3.fc
1240 4.fc
1148 5.fc
1160 6.fc
1156 7.fc
1160 8.fc
1160 9.fc