diff --git a/neutron/tests/unit/hyperv/test_hyperv_neutron_agent.py b/neutron/tests/unit/hyperv/test_hyperv_neutron_agent.py
index 816b763752..8d1252765e 100644
--- a/neutron/tests/unit/hyperv/test_hyperv_neutron_agent.py
+++ b/neutron/tests/unit/hyperv/test_hyperv_neutron_agent.py
@@ -54,7 +54,7 @@ class TestHyperVNeutronAgent(base.BaseTestCase):
 
         mock.patch('neutron.openstack.common.loopingcall.'
                    'FixedIntervalLoopingCall',
-                   new=MockFixedIntervalLoopingCall)
+                   new=MockFixedIntervalLoopingCall).start()
         cfg.CONF.set_default('firewall_driver',
                              'neutron.agent.firewall.NoopFirewallDriver',
                              group='SECURITYGROUP')