Troubles with MASTER_SITES

[Jona Joachim]

Hi!
I must be missing something obvious with MASTER_SITES.
If you consider the devel/tigcc port which I maintain you can read:

MASTER_SITES=		${MASTER_SITE_GCC}:gcc \
			${MASTER_SITE_GNU}:gas \
			http://tigcc.ticalc.org/linux/:tigcc
MASTER_SITE_SUBDIR=	snapshots/4.1-20060728/:gcc \
			binutils/:gas
DISTFILES=		gcc-core-4.1-20060728.tar.bz2:gcc \
			binutils-2.16.1.tar.bz2:gas \
			tigcc_src.tar.bz2:tigcc

I just got a mail from Bill Fenner saying that a distfile is not fetchable.
When I issue 'make fetch' the following happens:

/usr/ports/devel/tigcc> sudo make fetch
=> gcc-core-4.1-20060728.tar.bz2 doesn't seem to exist in
/usr/ports/distfiles/.
=> Attempting to fetch from
ftp://mirror.aarnet.edu.au/pub/gcc/snapshots/4.1-200 60728/.
fetch:
ftp://mirror.aarnet.edu.au/pub/gcc/snapshots/4.1-20060728/gcc-core-4.1-20
060728.tar.bz2: File unavailable (e.g., file not found, no access)
=> Attempting to fetch from
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/distfiles/.
gcc-core-4.1-20060728.tar.bz2                 100% of   14 MB  156 kBps
00m00s

It is true that the file is not present on the mirror.aarnet.edu.au
mirror but why doesn't it try to fetch it from elsewhere?
It is actually present on the gcc.gnu.org mirror.
mirror.aarnet.edu.au is actually the last mirror listed for
${MASTER_SITE_GCC} in bsd.sites.mk
Does anybody know what's going on?

Best regards,
Jona