TempalateVM build error: invalid tag

I’m trying to build an Ubuntu template VM following the guide. When trying to setup the builder using this guide, I get the following error in the make get-sources step.

-> Updating sources for mgmt-salt-base-config…
–> Fetching from https;//github;com/QubesOS/qubes-mgmt-salt-base-config.git release4.0 (options: --depth=1)…
–> Verifying tags…
gpg: keybox ‘/home/user/qubes-builder/keyrings/git/mgmt-salt-base-config/pubring.kbx’ created
gpg: key E2A783B8C37BB66B: 1 signature not checked due to a missing key
gpg: /home/user/qubes-builder/keyrings/git/mgmt-salt-base-config/trustdb.gpg: trustdb created
gpg: key E2A783B8C37BB66B: public key “Joanna Rutkowska (Qubes OS signing key) <joanna@invisiblethingslab;com>” imported

gpg: key DA0434BC706E1FCF: “Simon Gaiser (Qubes OS signing key) <simon@invisiblethingslab;com>” not changed
gpg: Total number processed: 15
gpg: unchanged: 15
No valid signed tag found!
—> One of invalid tag:
object 04bb8c9aaef7511a45111d428b17ab7a74500ac4
type commit
tag mm_04bb8c9a
tagger Marek Marczykowski-Górecki <marmarek@invisiblethingslab;com> 1571536184 +0200

Tag for commit 04bb8c9aaef7511a45111d428b17ab7a74500ac4
gpg: Signature made Sun Oct 20 03:49:45 2019 CEST
gpg: using RSA key 0064428F455451B3EBE78A7F063938BA42CFA724
gpg: Good signature from “Marek Marczykowski-Górecki (Qubes OS signing key) <marmarek@invisiblethingslab;com>” [full]
make: *** [Makefile:213: mgmt-salt-base-config.get-sources] Error 1

I’ve verified that the relevant key, 0064428F455451B3EBE78A7F063938BA42CFA724 is fully trusted and can’t see any other reason that tag should be invalid.

Can anyone explain how to remedy this problem?