diff --git a/xos/synchronizer/event_steps/test_auth_event.py b/xos/synchronizer/event_steps/test_auth_event.py
index e04f70b..5587940 100644
--- a/xos/synchronizer/event_steps/test_auth_event.py
+++ b/xos/synchronizer/event_steps/test_auth_event.py
@@ -107,5 +107,5 @@
 
             self.event_step.process_event(self.event)
 
-            self.hippie_si.save.assert_called_with(always_update_timestamp=True, update_fields=['authentication_state', 'updated'])
+            self.hippie_si.save.assert_called_with(always_update_timestamp=True, update_fields=['authentication_state', 'serial_number', 'updated'])
             self.assertEqual(self.hippie_si.authentication_state, 'APPROVED')