diff --git a/xos/synchronizer/models/models.py b/xos/synchronizer/models/models.py
index 3cd13f4..380d44c 100644
--- a/xos/synchronizer/models/models.py
+++ b/xos/synchronizer/models/models.py
@@ -129,6 +129,13 @@
     class Meta:
         proxy = True
 
+    def delete(self, *args, **kwargs):
+
+        if len(self.volt_service_instances.all()) > 0:
+            raise XOSValidationError('ONU "%s" can\'t be deleted as it has subscribers associated with it' % self.serial_number)
+
+        super(ONUDevice, self).delete(*args, **kwargs)
+
 class PONONUPort(PONONUPort_decl):
     class Meta:
         proxy = True
diff --git a/xos/synchronizer/models/test_oltdevice_model.py b/xos/synchronizer/models/test_models.py
similarity index 67%
rename from xos/synchronizer/models/test_oltdevice_model.py
rename to xos/synchronizer/models/test_models.py
index 5da9583..92a939b 100644
--- a/xos/synchronizer/models/test_oltdevice_model.py
+++ b/xos/synchronizer/models/test_models.py
@@ -45,6 +45,9 @@
         self.olt_device.is_new = True
         self.olt_device.device_id = 1234
 
+    def tearDown(self):
+        self.module_patcher.stop()
+
     def test_create_mac_address(self):
         from models import OLTDevice
         olt = OLTDevice()
@@ -84,5 +87,45 @@
             self.assertEqual(e.exception.message, 'OLT "1234" can\'t be deleted as it has subscribers associated with its ONUs')
             self.models_decl.OLTDevice_decl.delete.assert_not_called()
 
+class TestONUDeviceModel(unittest.TestCase):
+
+    def setUp(self):
+        self.xos = XOS
+
+        self.models_decl = Mock()
+        self.models_decl.ONUDevice_decl = MagicMock
+        self.models_decl.ONUDevice_decl.delete = Mock()
+
+        modules = {
+            'xos.exceptions': self.xos.exceptions,
+            'models_decl': self.models_decl,
+        }
+
+        self.module_patcher = patch.dict('sys.modules', modules)
+        self.module_patcher.start()
+
+        from models import ONUDevice
+
+        self.onu_device = ONUDevice()
+        self.onu_device.id = None  # this is a new model
+        self.onu_device.is_new = True
+        self.onu_device.serial_number = 1234
+
+    def test_delete(self):
+        self.onu_device.delete()
+        self.models_decl.ONUDevice_decl.delete.assert_called()
+
+    def test_prevent_delete(self):
+        volt_si_1 = Mock()
+        volt_si_1.onu_device_id = self.onu_device.id
+        self.onu_device.volt_service_instances.all.return_value = [volt_si_1]
+
+        with self.assertRaises(Exception) as e:
+            self.onu_device.delete()
+
+        self.assertEqual(e.exception.message,
+                         'ONU "1234" can\'t be deleted as it has subscribers associated with it')
+        self.models_decl.OLTDevice_decl.delete.assert_not_called()
+
 if __name__ == '__main__':
     unittest.main()