diff --git a/neutron/db/l3_db.py b/neutron/db/l3_db.py
index d0ddd80ba89..9cce345d1ed 100644
--- a/neutron/db/l3_db.py
+++ b/neutron/db/l3_db.py
@@ -87,8 +87,8 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
 
     _fip_qos = None
 
-    def __new__(cls):
-        inst = super(L3_NAT_dbonly_mixin, cls).__new__(cls)
+    def __new__(cls, *args, **kwargs):
+        inst = super(L3_NAT_dbonly_mixin, cls).__new__(cls, *args, **kwargs)
         inst._start_janitor()
         return inst
 
diff --git a/neutron/tests/unit/db/test_l3_db.py b/neutron/tests/unit/db/test_l3_db.py
index 7fd939cb93c..0f5ecdde5a3 100644
--- a/neutron/tests/unit/db/test_l3_db.py
+++ b/neutron/tests/unit/db/test_l3_db.py
@@ -42,6 +42,16 @@ class TestL3_NAT_dbonly_mixin(base.BaseTestCase):
         filtered = l3_db.L3_NAT_dbonly_mixin._each_port_having_fixed_ips(None)
         self.assertEqual([], list(filtered))
 
+    def test__new__passes_args(self):
+        class T(l3_db.L3_NAT_db_mixin):
+            def __init__(self, *args, **kwargs):
+                self.args = args
+                self.kwargs = kwargs
+
+        t = T(1, 2, a=3)
+        self.assertEqual((1, 2), t.args)
+        self.assertEqual({'a': 3}, t.kwargs)
+
     def test__each_port_having_fixed_ips(self):
         """Basic test that ports without fixed ips are filtered out"""
         ports = [{'id': 'a', 'fixed_ips': [mock.sentinel.fixedip]},