diff --git a/bin/tests/system/isctest/kasp.py b/bin/tests/system/isctest/kasp.py
index 255a5832cc..bf7b1d2573 100644
--- a/bin/tests/system/isctest/kasp.py
+++ b/bin/tests/system/isctest/kasp.py
@@ -952,6 +952,8 @@ def _check_signatures(
         zrrsig = False
     krrsig = not zrrsig
 
+    signer = fqdn.lower()
+
     for key in keys:
         if key.external:
             continue
@@ -963,7 +965,7 @@ def _check_signatures(
         alg = key.get_dnsalg()
         rtype = dns.rdatatype.to_text(covers)
 
-        expect = rf"IN RRSIG {rtype} {alg} (\d) (\d+) (\d+) (\d+) {key.tag} {fqdn}"
+        expect = rf"IN RRSIG {rtype} {alg} (\d) (\d+) (\d+) (\d+) {key.tag} {signer}"
 
         if zrrsig and zsigning:
             has_rrsig = False
@@ -1572,17 +1574,18 @@ def keydir_to_keylist(
     """
     if zone is None:
         zone = ""
+    zname = zone.lower()
 
     all_keys = []
     if keydir is None:
-        regex = rf"(K{zone}\.\+.*\+.*)\.key"
-        for filename in glob.glob(f"K{zone}.+*+*.key"):
+        regex = rf"(K{zname}\.\+.*\+.*)\.key"
+        for filename in glob.glob(f"K{zname}.+*+*.key"):
             match = re.match(regex, filename)
             if match is not None:
                 all_keys.append(Key(match.group(1)))
     else:
-        regex = rf"{keydir}/(K{zone}\.\+.*\+.*)\.key"
-        for filename in glob.glob(f"{keydir}/K{zone}.+*+*.key"):
+        regex = rf"{keydir}/(K{zname}\.\+.*\+.*)\.key"
+        for filename in glob.glob(f"{keydir}/K{zname}.+*+*.key"):
             match = re.match(regex, filename)
             if match is not None:
                 all_keys.append(Key(match.group(1), keydir))
diff --git a/bin/tests/system/kasp/ns3/named-fips.conf.j2 b/bin/tests/system/kasp/ns3/named-fips.conf.j2
index 9255779175..19f3683e40 100644
--- a/bin/tests/system/kasp/ns3/named-fips.conf.j2
+++ b/bin/tests/system/kasp/ns3/named-fips.conf.j2
@@ -20,6 +20,13 @@ zone "default.kasp" {
 	dnssec-policy "default";
 };
 
+/* The UPPER case: a zone with uppercase characters. */
+zone "UPPER.KASP" {
+	type primary;
+	file "upper.kasp.db";
+	dnssec-policy "default";
+};
+
 /* A zone with special characters. */
 zone {% raw %}"i-am.\":\;?&[]\@!\$*+,|=\.\(\)special.kasp."{% endraw %} {
         type primary;
diff --git a/bin/tests/system/kasp/ns3/setup.sh b/bin/tests/system/kasp/ns3/setup.sh
index 756c0af19c..74b985dbcd 100644
--- a/bin/tests/system/kasp/ns3/setup.sh
+++ b/bin/tests/system/kasp/ns3/setup.sh
@@ -56,12 +56,16 @@ for zn in default dnssec-keygen some-keys legacy-keys pregenerated \
 done
 
 #
-# Setup special zone
+# Setup special zones
 #
 zone="i-am.\":\;?&[]\@!\$*+,|=\.\(\)special.kasp."
 echo_i "setting up zone: $zone"
 cp template.db.in "i-am.special.kasp.db"
 
+zone="UPPER.KASP."
+echo_i "setting up zone: $zone"
+cp upper.kasp.db.in "upper.kasp.db"
+
 #
 # Set up RSASHA1 based zones
 #
diff --git a/bin/tests/system/kasp/ns3/upper.kasp.db.in b/bin/tests/system/kasp/ns3/upper.kasp.db.in
new file mode 100644
index 0000000000..13999f9dcf
--- /dev/null
+++ b/bin/tests/system/kasp/ns3/upper.kasp.db.in
@@ -0,0 +1,27 @@
+; Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+;
+; SPDX-License-Identifier: MPL-2.0
+;
+; This Source Code Form is subject to the terms of the Mozilla Public
+; License, v. 2.0.  If a copy of the MPL was not distributed with this
+; file, you can obtain one at https://mozilla.org/MPL/2.0/.
+;
+; See the COPYRIGHT file distributed with this work for additional
+; information regarding copyright ownership.
+
+$TTL 300
+UPPER.KASP.	IN	SOA  MNAME1. . (
+			1       ; serial
+			20      ; refresh (20 seconds)
+			20      ; retry (20 seconds)
+			1814400 ; expire (3 weeks)
+			3600    ; minimum (1 hour)
+			)
+
+			NS	ns3
+ns3			A	10.53.0.3
+
+a			A	10.0.0.1
+b			A	10.0.0.2
+c			A	10.0.0.3
+
diff --git a/bin/tests/system/kasp/tests_kasp.py b/bin/tests/system/kasp/tests_kasp.py
index f5a02152dc..60dd34c800 100644
--- a/bin/tests/system/kasp/tests_kasp.py
+++ b/bin/tests/system/kasp/tests_kasp.py
@@ -936,6 +936,42 @@ def test_kasp_default(ns3):
     check_all(ns3, zone, policy, keys, [])
 
 
+def test_kasp_uppercase(ns3):
+    # check the zone with uppercase characters is loaded and signed.
+    isctest.log.info("check a zone with upper case characters is signed")
+    zone = "UPPER.KASP"
+    policy = "default"
+
+    isctest.kasp.wait_keymgr_done(ns3, zone)
+
+    # Key properties.
+    # DNSKEY, RRSIG (ksk), RRSIG (zsk) are published. DS needs to wait.
+    keyprops = [
+        "csk 0 13 256 goal:omnipresent dnskey:rumoured krrsig:rumoured zrrsig:rumoured ds:hidden",
+    ]
+    expected = isctest.kasp.policy_to_properties(ttl=3600, keys=keyprops)
+    keys = isctest.kasp.keydir_to_keylist(zone, "ns3")
+    isctest.kasp.check_dnssec_verify(ns3, zone)
+    isctest.kasp.check_keys(zone, keys, expected)
+    set_keytimes_default_policy(expected[0])
+    isctest.kasp.check_keytimes(keys, expected)
+    check_all(ns3, zone, policy, keys, [])
+
+    fqdn = f"{zone}."
+    query = isctest.query.create(fqdn, dns.rdatatype.NSEC)
+    response = isctest.query.tcp(query, ns3.ip)
+    assert response.rcode() == dns.rcode.NOERROR
+
+    nsec = response.get_rrset(
+        response.answer,
+        dns.name.from_text(fqdn),
+        dns.rdataclass.IN,
+        dns.rdatatype.NSEC,
+    )
+    nextname = nsec[0].next
+    assert str(nextname) == "a.upper.kasp."
+
+
 def test_kasp_dynamic(ns3):
     # Standard dynamic zone.
     isctest.log.info("check dynamic zone is updated and signed after update")