diff --git a/nova/conductor/manager.py b/nova/conductor/manager.py
index 87d98f2cadde..318cb0ec81dc 100644
--- a/nova/conductor/manager.py
+++ b/nova/conductor/manager.py
@@ -712,8 +712,11 @@ class ComputeTaskManager(base.Base):
                     # RequestSpec object - probably because the instance is old
                     # We need to mock that the old way
                     filter_properties = {'ignore_hosts': [instance.host]}
+                    # build_request_spec expects a primitive image dict
+                    image_meta = nova_object.obj_to_primitive(
+                        instance.image_meta)
                     request_spec = scheduler_utils.build_request_spec(
-                            context, image_ref, [instance])
+                            context, image_meta, [instance])
                 elif recreate:
                     # NOTE(sbauza): Augment the RequestSpec object by excluding
                     # the source host for avoiding the scheduler to pick it
diff --git a/nova/tests/unit/conductor/test_conductor.py b/nova/tests/unit/conductor/test_conductor.py
index a90a1ae75090..66105ba0192e 100644
--- a/nova/tests/unit/conductor/test_conductor.py
+++ b/nova/tests/unit/conductor/test_conductor.py
@@ -1239,6 +1239,9 @@ class _BaseTaskTestCase(object):
             self.conductor_manager.rebuild_instance(context=self.context,
                                             instance=inst_obj,
                                             **rebuild_args)
+            bs_mock.assert_called_once_with(
+                self.context, obj_base.obj_to_primitive(inst_obj.image_meta),
+                [inst_obj])
             fp_mock.assert_called_once_with(self.context, request_spec,
                                             filter_properties)
             select_dest_mock.assert_called_once_with(self.context, fake_spec)