diff --git a/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ovs_bridge.py b/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ovs_bridge.py
index 14be2687148..f639cd47f66 100644
--- a/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ovs_bridge.py
+++ b/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ovs_bridge.py
@@ -42,10 +42,12 @@ class OVSAgentBridge(ofswitch.OpenFlowSwitchMixin,
         """
         while True:
             if self._cached_dpid is None:
-                dpid_str = self.get_datapath_id()
+                dpid = self.get_datapath_id()
                 LOG.info("Bridge %(br_name)s has datapath-ID %(dpid)s",
-                         {"br_name": self.br_name, "dpid": dpid_str})
-                self._cached_dpid = int(dpid_str, 16)
+                         {"br_name": self.br_name, "dpid": dpid})
+                if dpid is None:
+                    raise RuntimeError("Unknown datapath id.")
+                self._cached_dpid = int(dpid, 16)
             try:
                 dp = self._get_dp_by_dpid(self._cached_dpid)
                 return dp, dp.ofproto, dp.ofproto_parser
diff --git a/neutron/tests/unit/plugins/ml2/drivers/openvswitch/agent/openflow/native/test_ovs_bridge.py b/neutron/tests/unit/plugins/ml2/drivers/openvswitch/agent/openflow/native/test_ovs_bridge.py
index b022c067db5..438a61d7528 100644
--- a/neutron/tests/unit/plugins/ml2/drivers/openvswitch/agent/openflow/native/test_ovs_bridge.py
+++ b/neutron/tests/unit/plugins/ml2/drivers/openvswitch/agent/openflow/native/test_ovs_bridge.py
@@ -49,3 +49,8 @@ class OVSAgentBridgeTestCase(ovs_test_base.OVSRyuTestBase):
         # make sure that in case of any misconfiguration when no datapath is
         # found a proper exception, not a TypeError is raised
         self.assertRaises(RuntimeError, br._get_dp)
+
+    def test__get_dp_when_get_datapath_id_returns_None(self):
+        br = self.br_int_cls('br-int')
+        with mock.patch.object(br, 'get_datapath_id', return_value=None):
+            self.assertRaises(RuntimeError, br._get_dp)