diff --git a/lower-constraints.txt b/lower-constraints.txt
index c2a27a41d..6860ddc09 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -79,7 +79,7 @@ oslo.cache==1.26.0
 oslo.concurrency==3.26.0
 oslo.config==6.1.0
 oslo.context==2.19.2
-oslo.db==4.27.0
+oslo.db==4.40.0
 oslo.i18n==3.15.3
 oslo.log==3.36.0
 oslo.messaging==6.3.0
diff --git a/nova/db/sqlalchemy/api.py b/nova/db/sqlalchemy/api.py
index a67747e40..59f0a8c29 100644
--- a/nova/db/sqlalchemy/api.py
+++ b/nova/db/sqlalchemy/api.py
@@ -202,7 +202,7 @@ def select_db_reader_mode(f):
         use_slave = keyed_args.get('use_slave', False)
 
         if use_slave:
-            reader_mode = get_context_manager(context).async
+            reader_mode = get_context_manager(context).async_
         else:
             reader_mode = get_context_manager(context).reader
 
diff --git a/requirements.txt b/requirements.txt
index 8e31a31d0..ce3fb5718 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -43,7 +43,7 @@ oslo.log>=3.36.0 # Apache-2.0
 oslo.reports>=1.18.0 # Apache-2.0
 oslo.serialization!=2.19.1,>=2.18.0 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0
-oslo.db>=4.27.0 # Apache-2.0
+oslo.db>=4.40.0 # Apache-2.0
 oslo.rootwrap>=5.8.0 # Apache-2.0
 oslo.messaging>=6.3.0 # Apache-2.0
 oslo.policy>=1.35.0 # Apache-2.0