diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index cfaf3f3a669b..c98a7d12474c 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -7731,7 +7731,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             conn.init_host("wibble")
             conn.get_num_instances()
             self.assertTrue(not service_mock.disabled and
-                            service_mock.disabled_reason is 'None')
+                            service_mock.disabled_reason is None)
 
     def test_immediate_delete(self):
         def fake_lookup_by_name(instance_name):
diff --git a/nova/tests/unit/virt/test_virt_drivers.py b/nova/tests/unit/virt/test_virt_drivers.py
index 6bda091980f7..998ecf2cbb72 100644
--- a/nova/tests/unit/virt/test_virt_drivers.py
+++ b/nova/tests/unit/virt/test_virt_drivers.py
@@ -840,7 +840,7 @@ class LibvirtConnTestCase(_VirtDriverTestCase, test.TestCase):
                                return_value=service_mock):
             self.connection._set_host_enabled(True)
             self.assertFalse(service_mock.disabled)
-            self.assertEqual(service_mock.disabled_reason, 'None')
+            self.assertIsNone(service_mock.disabled_reason)
 
     def test_set_host_enabled_when_manually_disabled(self):
         self.mox.UnsetStubs()
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index eb923133e139..e4faa112fd01 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -283,7 +283,7 @@ MAX_CONSOLE_BYTES = 100 * units.Ki
 # The libvirt driver will prefix any disable reason codes with this string.
 DISABLE_PREFIX = 'AUTO: '
 # Disable reason for the service which was enabled or disabled without reason
-DISABLE_REASON_UNDEFINED = 'None'
+DISABLE_REASON_UNDEFINED = None
 
 # Guest config console string
 CONSOLE = "console=tty0 console=ttyS0"
@@ -509,8 +509,6 @@ class LibvirtDriver(driver.ComputeDriver):
     def _handle_conn_event(self, enabled, reason):
         LOG.info(_LI("Connection event '%(enabled)d' reason '%(reason)s'"),
                  {'enabled': enabled, 'reason': reason})
-        if reason is None:
-            reason = DISABLE_REASON_UNDEFINED
         self._set_host_enabled(enabled, reason)
 
     def init_host(self, host):