diff --git a/neutron/notifiers/nova.py b/neutron/notifiers/nova.py
index 2b2bab63d1..e95100597a 100644
--- a/neutron/notifiers/nova.py
+++ b/neutron/notifiers/nova.py
@@ -132,6 +132,18 @@ class Notifier(object):
         if not cfg.CONF.notify_nova_on_port_data_changes:
             return
 
+        # When neutron re-assigns floating ip from an original instance
+        # port to a new instance port without disassociate it first, an
+        # event should be sent for original instance, that will make nova
+        # know original instance's info, and update database for it.
+        if (action == 'update_floatingip'
+                and returned_obj['floatingip'].get('port_id')
+                and original_obj.get('port_id')):
+            disassociate_returned_obj = {'floatingip': {'port_id': None}}
+            event = self.create_port_changed_event(action, original_obj,
+                                                   disassociate_returned_obj)
+            self.queue_event(event)
+
         event = self.create_port_changed_event(action, original_obj,
                                                returned_obj)
         self.queue_event(event)
diff --git a/neutron/tests/unit/notifiers/test_notifiers_nova.py b/neutron/tests/unit/notifiers/test_notifiers_nova.py
index 7972ebf55a..db9bc79c31 100644
--- a/neutron/tests/unit/notifiers/test_notifiers_nova.py
+++ b/neutron/tests/unit/notifiers/test_notifiers_nova.py
@@ -303,3 +303,20 @@ class TestNovaNotify(base.BaseTestCase):
                 self.nova_notifier.queue_event(mock.Mock())
                 self.assertFalse(self.nova_notifier._waiting_to_send)
                 send_events.assert_called_once_with()
+
+    def test_reassociate_floatingip_without_disassociate_event(self):
+        returned_obj = {'floatingip':
+                        {'port_id': 'f5348a16-609a-4971-b0f0-4b8def5235fb'}}
+        original_obj = {'port_id': '5a39def4-3d3f-473d-9ff4-8e90064b9cc1'}
+        self.nova_notifier._waiting_to_send = True
+        self.nova_notifier.send_network_change(
+            'update_floatingip', original_obj, returned_obj)
+        self.assertEqual(2, len(self.nova_notifier.pending_events))
+
+        returned_obj_non = {'floatingip': {'port_id': None}}
+        event_dis = self.nova_notifier.create_port_changed_event(
+            'update_floatingip', original_obj, returned_obj_non)
+        event_assoc = self.nova_notifier.create_port_changed_event(
+            'update_floatingip', original_obj, returned_obj)
+        self.assertEqual(self.nova_notifier.pending_events[0], event_dis)
+        self.assertEqual(self.nova_notifier.pending_events[1], event_assoc)