freebsd-update metadata signature for 13.1-R not found

Hi,

Attempting to upgrade a 13.0-p8 (amd64) machine to 13.1-R gives the following output:

[...]

# freebsd-update upgrade -r 13.1-RELEASE
src component not installed, skipped
Looking up update.FreeBSD.org mirrors... 2 mirrors found.
Fetching metadata signature for 13.0-RELEASE from update1.freebsd.org... done.
Fetching metadata index... done.
Fetching 1 metadata files... done.
Inspecting system... done.

The following components of FreeBSD seem to be installed:
kernel/generic kernel/generic-dbg world/base world/base-dbg world/lib32
world/lib32-dbg

The following components of FreeBSD do not seem to be installed:

Does this look reasonable (y/n)? y

Fetching metadata signature for 13.1-RELEASE from update1.freebsd.org... failed.
Fetching metadata signature for 13.1-RELEASE from update2.freebsd.org... failed.
No mirrors remaining, giving up.

This may be because upgrading from this platform (amd64)
or release (13.1-RELEASE) is unsupported by freebsd-update. Only
platforms with Tier 1 support can be upgraded by freebsd-update.
See https://www.freebsd.org/platforms/index.html for more info.

If unsupported, FreeBSD must be upgraded by source.

[...]

# uname -vKU
FreeBSD 13.0-RELEASE-p8 #0: Tue Mar 15 09:36:28 UTC 2022     root@amd64-builder.daemonology.net:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  1300139 1300139

# host update1.freebsd.org
update1.freebsd.org has address 163.237.247.16
update1.freebsd.org has IPv6 address 2001:4978:1000::2319:16
update1.freebsd.org mail is handled by 0 .

# host update2.freebsd.org
update2.freebsd.org has address 204.15.11.69
update2.freebsd.org has IPv6 address 2620:11c:5001:1099:1337::117
update2.freebsd.org mail is handled by 0 .

# fping update1.freebsd.org
update1.freebsd.org is alive

# fping update2.freebsd.org
update2.freebsd.org is alive

-- 
J.