diff --git a/tests/openpgp/issue5120.scm b/tests/openpgp/issue5120.scm
new file mode 100644
index 000000000..119d5f69a
--- /dev/null
+++ b/tests/openpgp/issue5120.scm
@@ -0,0 +1,69 @@
+#!/usr/bin/env gpgscm
+
+;; Regression tests for importing/signing Ed25519 keys which are
+;; related to SOS representations, for issue 5120 and 5953.
+
+;; Copyright (C) 2022 g10 Code GmbH
+;;
+;; This file is part of GnuPG.
+;;
+;; GnuPG is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3 of the License, or
+;; (at your option) any later version.
+;;
+;; GnuPG is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+;;
+;; You should have received a copy of the GNU General Public License
+;; along with this program; if not, see <http://www.gnu.org/licenses/>.
+
+(load (in-srcdir "tests" "openpgp" "defs.scm"))
+(setup-legacy-environment)
+
+;; A secret key made by SOS representation having leading-zeros
+(define secret-key-non-protected-0 "-----BEGIN PGP PRIVATE KEY BLOCK-----
+
+lFgEW9rRAxYJKwYBBAHaRw8BAQdAAAAfi+pCs8dMUKo1ibGqBl8ZaFfbl6deSlSV
+Pwk+Z3IAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAJAAltBpTYXZl
+IE91ciBMZWFkaW5nIFplcm9zIDA5OYiaBBMWCgBCFiEE8sEmTikqKYrrS8NIYDMV
+yTB5KUAFAlva0QMCGwMFCQPCZwAFCwkIBwIDIgIBBhUKCQgLAgQWAgMBAh4HAheA
+AAoJEGAzFckweSlAQ84BAACkDMCCuSYRgXddPF3DZFNBV71nvSFiWJwEJ1FPOWwe
+AP0RRuStMwJ/PhNcnYcRk7cSUQFUanHaCUvZs/flY9VjCw==
+=muKZ
+-----END PGP PRIVATE KEY BLOCK-----")
+
+(pipe:do
+ (pipe:echo secret-key-non-protected-0)
+ (pipe:gpg '(--import)))
+
+(pipe:do
+ (pipe:echo "Please sign")
+ (pipe:gpg '(--faked-system-time=1541067011
+             --local-user "Save Our Leading Zeros 099" --armor --detach-sign)))
+
+;; Another secret key having leading-bit 1
+(define secret-key-non-protected-1 "-----BEGIN PGP PRIVATE KEY BLOCK-----
+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+=l6au
+-----END PGP PRIVATE KEY BLOCK-----")
+
+(pipe:do
+ (pipe:echo secret-key-non-protected-1)
+ (pipe:gpg '(--import)))
+
+(pipe:do
+ (pipe:echo "test")
+ (pipe:gpg '(--local-user "test key" --armor --detach-sign)))