diff --git a/xos/synchronizer/model_policies/model_policy_voltserviceinstance.py b/xos/synchronizer/model_policies/model_policy_voltserviceinstance.py
index 966435a..c437c78 100644
--- a/xos/synchronizer/model_policies/model_policy_voltserviceinstance.py
+++ b/xos/synchronizer/model_policies/model_policy_voltserviceinstance.py
@@ -68,4 +68,4 @@
             raise Exception("ONUDevice with serial number %s can't be found" % onu_device_serial_number)
 
         si.onu_device_id = onu.id
-        si.save()
+        si.save_changed_fields()
diff --git a/xos/synchronizer/model_policies/test_model_policy_voltserviceinstance.py b/xos/synchronizer/model_policies/test_model_policy_voltserviceinstance.py
index 3ded41d..1cfdf05 100644
--- a/xos/synchronizer/model_policies/test_model_policy_voltserviceinstance.py
+++ b/xos/synchronizer/model_policies/test_model_policy_voltserviceinstance.py
@@ -129,7 +129,7 @@
             self.policy.associate_onu_device(self.si)
 
             self.assertEqual(self.si.onu_device_id, mock_onu.id)
-            self.si.save.assert_called()
+            self.si.save_changed_fields.assert_called()
 
     def test_handle_delete(self):
         self.policy.handle_delete(self.si)