diff --git a/src/flask/app.py b/src/flask/app.py
index 72dea7bb..9a6fdd40 100644
--- a/src/flask/app.py
+++ b/src/flask/app.py
@@ -1411,8 +1411,8 @@ class Flask(App):
                 for func in reversed(self.after_request_funcs[name]):
                     response = self.ensure_sync(func)(response)
 
-        if not self.session_interface.is_null_session(ctx._session):
-            self.session_interface.save_session(self, ctx._session, response)
+        if not self.session_interface.is_null_session(ctx._get_session()):
+            self.session_interface.save_session(self, ctx._get_session(), response)
 
         return response