diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index ae53984a13ab..95a35565c119 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -442,6 +442,11 @@ def object_compat(function):
     def decorated_function(self, context, *args, **kwargs):
         def _load_instance(instance_or_dict):
             if isinstance(instance_or_dict, dict):
+                # try to get metadata and system_metadata for most cases but
+                # only attempt to load those if the db instance already has
+                # those fields joined
+                metas = [meta for meta in ('metadata', 'system_metadata')
+                         if meta in instance_or_dict]
                 instance = objects.Instance._from_db_object(
                     context, objects.Instance(), instance_or_dict,
                     expected_attrs=metas)
@@ -449,7 +454,6 @@ def object_compat(function):
                 return instance
             return instance_or_dict
 
-        metas = ['metadata', 'system_metadata']
         try:
             kwargs['instance'] = _load_instance(kwargs['instance'])
         except KeyError:
diff --git a/nova/tests/unit/compute/test_compute.py b/nova/tests/unit/compute/test_compute.py
index d5ae8c82de08..f76ccaab0a01 100644
--- a/nova/tests/unit/compute/test_compute.py
+++ b/nova/tests/unit/compute/test_compute.py
@@ -1352,6 +1352,24 @@ class ComputeTestCase(BaseTestCase):
         def test_fn(_self, context, instance):
             self.assertIsInstance(instance, objects.Instance)
             self.assertEqual(instance.uuid, db_inst['uuid'])
+            self.assertEqual(instance.metadata, db_inst['metadata'])
+            self.assertEqual(instance.system_metadata,
+                             db_inst['system_metadata'])
+        test_fn(None, self.context, instance=db_inst)
+
+    def test_object_compat_no_metas(self):
+        # Tests that we don't try to set metadata/system_metadata on the
+        # instance object using fields that aren't in the db object.
+        db_inst = fake_instance.fake_db_instance()
+        db_inst.pop('metadata', None)
+        db_inst.pop('system_metadata', None)
+
+        @compute_manager.object_compat
+        def test_fn(_self, context, instance):
+            self.assertIsInstance(instance, objects.Instance)
+            self.assertEqual(instance.uuid, db_inst['uuid'])
+            self.assertNotIn('metadata', instance)
+            self.assertNotIn('system_metadata', instance)
         test_fn(None, self.context, instance=db_inst)
 
     def test_object_compat_more_positional_args(self):
@@ -1361,6 +1379,9 @@ class ComputeTestCase(BaseTestCase):
         def test_fn(_self, context, instance, pos_arg_1, pos_arg_2):
             self.assertIsInstance(instance, objects.Instance)
             self.assertEqual(instance.uuid, db_inst['uuid'])
+            self.assertEqual(instance.metadata, db_inst['metadata'])
+            self.assertEqual(instance.system_metadata,
+                             db_inst['system_metadata'])
             self.assertEqual(pos_arg_1, 'fake_pos_arg1')
             self.assertEqual(pos_arg_2, 'fake_pos_arg2')