diff --git a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
index 2759a3c8162..66171023fae 100644
--- a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
+++ b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
@@ -1539,16 +1539,17 @@ class TestOVNMechanismDriver(test_plugin.Ml2PluginV2TestCase):
             fake_context, fake_port['id'], const.PORT_STATUS_ACTIVE)
 
     def _add_chassis_agent(self, nb_cfg, agent_type, updated_at=None):
+        updated_at = updated_at or datetime.datetime.utcnow()
         chassis = mock.Mock()
         chassis.nb_cfg = nb_cfg
         chassis.uuid = uuid.uuid4()
         chassis.external_ids = {ovn_const.OVN_LIVENESS_CHECK_EXT_ID_KEY:
-                                timeutils.isotime(updated_at)}
+                                datetime.datetime.isoformat(updated_at)}
         if agent_type == ovn_const.OVN_METADATA_AGENT:
             chassis.external_ids.update({
                 ovn_const.OVN_AGENT_METADATA_SB_CFG_KEY: nb_cfg,
                 ovn_const.METADATA_LIVENESS_CHECK_EXT_ID_KEY:
-                timeutils.isotime(updated_at)})
+                datetime.datetime.isoformat(updated_at)})
 
         return chassis