diff --git a/nova/db/sqlalchemy/api_migrations/migrate_repo/versions/062_instance_mapping_add_user_id.py b/nova/db/sqlalchemy/api_migrations/migrate_repo/versions/062_instance_mapping_add_user_id.py
new file mode 100644
index 000000000000..34ea9c603036
--- /dev/null
+++ b/nova/db/sqlalchemy/api_migrations/migrate_repo/versions/062_instance_mapping_add_user_id.py
@@ -0,0 +1,32 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from sqlalchemy import Column
+from sqlalchemy import Index
+from sqlalchemy import MetaData
+from sqlalchemy import String
+from sqlalchemy import Table
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    instance_mappings = Table('instance_mappings', meta, autoload=True)
+
+    if not hasattr(instance_mappings.c, 'user_id'):
+        instance_mappings.create_column(Column('user_id', String(length=255),
+            nullable=True))
+        index = Index('instance_mappings_user_id_project_id_idx',
+                      instance_mappings.c.user_id,
+                      instance_mappings.c.project_id)
+        index.create()
diff --git a/nova/db/sqlalchemy/api_models.py b/nova/db/sqlalchemy/api_models.py
index 442ad3cb3048..609a75e2f452 100644
--- a/nova/db/sqlalchemy/api_models.py
+++ b/nova/db/sqlalchemy/api_models.py
@@ -134,13 +134,18 @@ class InstanceMapping(API_BASE):
     __table_args__ = (Index('project_id_idx', 'project_id'),
                       Index('instance_uuid_idx', 'instance_uuid'),
                       schema.UniqueConstraint('instance_uuid',
-                          name='uniq_instance_mappings0instance_uuid'))
+                          name='uniq_instance_mappings0instance_uuid'),
+                      Index('instance_mappings_user_id_project_id_idx',
+                            'user_id', 'project_id'))
 
     id = Column(Integer, primary_key=True)
     instance_uuid = Column(String(36), nullable=False)
     cell_id = Column(Integer, ForeignKey('cell_mappings.id'),
             nullable=True)
     project_id = Column(String(255), nullable=False)
+    # FIXME(melwitt): This should eventually be non-nullable, but we need a
+    # transition period first.
+    user_id = Column(String(255), nullable=True)
     queued_for_delete = Column(Boolean)
     cell_mapping = orm.relationship('CellMapping',
             backref=backref('instance_mapping', uselist=False),
diff --git a/nova/tests/functional/db/api/test_migrations.py b/nova/tests/functional/db/api/test_migrations.py
index f9c7f82835e9..108be5af4d71 100644
--- a/nova/tests/functional/db/api/test_migrations.py
+++ b/nova/tests/functional/db/api/test_migrations.py
@@ -726,6 +726,11 @@ class NovaAPIMigrationsWalk(test_migrations.WalkVersionsMixin):
         self.assertColumnExists(engine, 'instance_mappings',
             'queued_for_delete')
 
+    def _check_062(self, engine, data):
+        self.assertColumnExists(engine, 'instance_mappings', 'user_id')
+        self.assertIndexExists(engine, 'instance_mappings',
+                               'instance_mappings_user_id_project_id_idx')
+
 
 class TestNovaAPIMigrationsWalkSQLite(NovaAPIMigrationsWalk,
                                       test_fixtures.OpportunisticDBTestMixin,