diff --git a/neutron/db/l3_agentschedulers_db.py b/neutron/db/l3_agentschedulers_db.py
index cb8206b74ce..4397d9e225f 100644
--- a/neutron/db/l3_agentschedulers_db.py
+++ b/neutron/db/l3_agentschedulers_db.py
@@ -385,6 +385,8 @@ class L3AgentSchedulerDbMixin(l3agentscheduler.L3AgentSchedulerPluginBase,
         ports on the host, running the input l3agent.
         """
         subnet_ids = self.get_subnet_ids_on_router(context, router_id)
+        if not subnet_ids:
+            return False
 
         core_plugin = manager.NeutronManager.get_plugin()
         filter = {'fixed_ips': {'subnet_id': subnet_ids}}
diff --git a/neutron/tests/unit/test_l3_schedulers.py b/neutron/tests/unit/test_l3_schedulers.py
index f3ba89e80b0..ef548a167e1 100644
--- a/neutron/tests/unit/test_l3_schedulers.py
+++ b/neutron/tests/unit/test_l3_schedulers.py
@@ -667,33 +667,45 @@ class L3SchedulerTestBaseMixin(object):
 
     def test_check_ports_exist_on_l3agent_no_subnets(self):
         l3_agent, router = self._prepare_check_ports_exist_tests()
-        # no subnets
-        val = self.check_ports_exist_on_l3agent(self.adminContext,
-                                                l3_agent, router['id'])
-        self.assertFalse(val)
+        with mock.patch.object(manager.NeutronManager,
+                               'get_plugin') as getp:
+            getp.return_value = self.plugin
+            # no subnets
+            self.get_subnet_ids_on_router.return_value = set()
+            val = self.check_ports_exist_on_l3agent(self.adminContext,
+                                                    l3_agent, router['id'])
+            self.assertFalse(self.plugin.get_ports.called)
+            self.assertFalse(val)
 
     def test_check_ports_exist_on_l3agent_no_subnet_match(self):
         l3_agent, router = self._prepare_check_ports_exist_tests()
-        # no matching subnet
-        self.plugin.get_subnet_ids_on_router = mock.Mock(
-            return_value=[str(uuid.uuid4())])
-        val = self.check_ports_exist_on_l3agent(self.adminContext,
-                                                l3_agent, router['id'])
-        self.assertFalse(val)
+        with mock.patch.object(manager.NeutronManager,
+                               'get_plugin') as getp:
+            getp.return_value = self.plugin
+            # no matching subnet
+            self.get_subnet_ids_on_router.return_value = [str(uuid.uuid4())]
+            val = self.check_ports_exist_on_l3agent(self.adminContext,
+                                                    l3_agent, router['id'])
+            self.assertTrue(self.plugin.get_ports.called)
+            self.assertFalse(val)
 
     def test_check_ports_exist_on_l3agent_subnet_match(self):
         l3_agent, router = self._prepare_check_ports_exist_tests()
-        # matching subnet
-        port = {'subnet_id': str(uuid.uuid4()),
-                'binding:host_id': 'host_1',
-                'device_owner': 'compute:',
-                'id': 1234}
-        self.plugin.get_ports.return_value = [port]
-        self.plugin.get_subnet_ids_on_router = mock.Mock(
-            return_value=[port['subnet_id']])
-        val = self.check_ports_exist_on_l3agent(self.adminContext,
-                                                l3_agent, router['id'])
-        self.assertTrue(val)
+        with mock.patch.object(manager.NeutronManager,
+                               'get_plugin') as getp:
+            getp.return_value = self.plugin
+            # matching subnet
+            port = {'subnet_id': str(uuid.uuid4()),
+                    'binding:host_id': 'host_1',
+                    'device_owner': 'compute:',
+                    'id': 1234}
+            self.plugin.get_ports.return_value = [port]
+            self.get_subnet_ids_on_router = mock.Mock(
+                return_value=[port['subnet_id']])
+            val = self.check_ports_exist_on_l3agent(self.adminContext,
+                                                    l3_agent, router['id'])
+            self.assertTrue(self.plugin.get_ports.called)
+            self.assertTrue(val)
 
 
 class L3SchedulerTestCase(l3_agentschedulers_db.L3AgentSchedulerDbMixin,