diff --git a/neutron/services/revisions/revision_plugin.py b/neutron/services/revisions/revision_plugin.py
index 24e2e7f7f7e..28e5e91c904 100644
--- a/neutron/services/revisions/revision_plugin.py
+++ b/neutron/services/revisions/revision_plugin.py
@@ -78,14 +78,14 @@ class RevisionPlugin(service_base.ServicePluginBase):
     def bump_revisions(self, session, context, instances):
         self._enforce_if_match_constraints(session)
         # bump revision number for updated objects in the session
+        modified_objs = {o for o in session.dirty if session.is_modified(o)}
         self._bump_obj_revisions(
-            session,
-            self._get_objects_to_bump_revision(session.dirty))
+            session, self._get_objects_to_bump_revision(modified_objs))
 
         # see if any created/updated/deleted objects bump the revision
         # of another object
         objects_with_related_revisions = [
-            o for o in session.deleted | session.dirty | session.new
+            o for o in modified_objs | set(session.deleted) | set(session.new)
             if getattr(o, 'revises_on_change', ())
         ]
         collected = session.info.setdefault('_related_bumped', set())
diff --git a/neutron/tests/unit/services/revisions/test_revision_plugin.py b/neutron/tests/unit/services/revisions/test_revision_plugin.py
index 8f5ae05916d..7d9cc9a5ddd 100644
--- a/neutron/tests/unit/services/revisions/test_revision_plugin.py
+++ b/neutron/tests/unit/services/revisions/test_revision_plugin.py
@@ -143,13 +143,13 @@ class TestRevisionPlugin(test_plugin.Ml2PluginV2TestCase):
         # update
         with self.port() as port:
             rev = port['port']['revision_number']
-            new = {'port': {'name': 'nigiri'}}
 
             def concurrent_increment(s):
                 db_api.sqla_remove(se.Session, 'before_commit',
                                    concurrent_increment)
                 # slip in a concurrent update that will bump the revision
                 plugin = directory.get_plugin()
+                new = {'port': {'name': 'nigiri'}}
                 plugin.update_port(nctx.get_admin_context(),
                                    port['port']['id'], new)
                 raise db_exc.DBDeadlock()
@@ -160,13 +160,16 @@ class TestRevisionPlugin(test_plugin.Ml2PluginV2TestCase):
             # transaction, the revision number is tested only once the first
             # time the revision number service is executed for this session and
             # object.
+            new = {'port': {'name': 'sushi'}}
             self._update('ports', port['port']['id'], new,
                          headers={'If-Match': 'revision_number=%s' % rev},
                          expected_code=exc.HTTPOk.code)
+            new = {'port': {'name': 'salmon'}}
             self._update('ports', port['port']['id'], new,
                          headers={'If-Match': 'revision_number=%s' %
                                               str(int(rev) + 2)},
                          expected_code=exc.HTTPOk.code)
+            new = {'port': {'name': 'tea'}}
             self._update('ports', port['port']['id'], new,
                          headers={'If-Match': 'revision_number=1'},
                          expected_code=exc.HTTPPreconditionFailed.code)