diff --git a/tests/scripts/thread-cert/border_router/test_dnssd_instance_name_with_space.py b/tests/scripts/thread-cert/border_router/test_dnssd_instance_name_with_space.py
index e6ac3613e..1e3bbcb69 100644
--- a/tests/scripts/thread-cert/border_router/test_dnssd_instance_name_with_space.py
+++ b/tests/scripts/thread-cert/border_router/test_dnssd_instance_name_with_space.py
@@ -115,6 +115,7 @@ class TestDnssdInstanceNameWithSpace(thread_cert.TestCase):
 
         self._verify_service_browse_result(client.dns_browse(SERVICE_FULL_NAME, server=br1.get_rloc()))
         self._verify_service_browse_result(client.dns_browse(SERVICE_FULL_NAME, server=br2.get_rloc()))
+        self._verify_service_browse_result(client.dns_browse(SERVICE_FULL_NAME.lower(), server=br2.get_rloc()))
 
         # check if PTR query works
         dig_result = digger.dns_dig(server_addr, SERVICE_FULL_NAME, 'PTR')
diff --git a/tests/scripts/thread-cert/test_dnssd_name_with_special_chars.py b/tests/scripts/thread-cert/test_dnssd_name_with_special_chars.py
index 5c9f96c6f..1d1393e4d 100644
--- a/tests/scripts/thread-cert/test_dnssd_name_with_special_chars.py
+++ b/tests/scripts/thread-cert/test_dnssd_name_with_special_chars.py
@@ -103,6 +103,9 @@ class TestDnssdNameWithSpecialChars(thread_cert.TestCase):
         service = client.dns_resolve_service(SPECIAL_INSTANCE_NAME, '_srv._udp.default.service.arpa')
         self.__verify_service(service)
 
+        service = client.dns_resolve_service(SPECIAL_INSTANCE_NAME.lower(), '_srv._udp.default.service.arpa')
+        self.__verify_service(service)
+
     def __verify_service(self, service):
         logging.info('service discovered: %r', service)
         self.assertEqual(service['port'], 1977)