diff --git a/src/flask/sessions.py b/src/flask/sessions.py
index ee19ad63..05b367a2 100644
--- a/src/flask/sessions.py
+++ b/src/flask/sessions.py
@@ -365,10 +365,10 @@ class SecureCookieSessionInterface(SessionInterface):
             return
 
         expires = self.get_expiration_time(app, session)
-        val = self.get_signing_serializer(app).dumps(dict(session))  # type: ignore
+        val = self.get_signing_serializer(app).dumps(dict(session))  # type: ignore[union-attr]
         response.set_cookie(
             name,
-            val,  # type: ignore
+            val,
             expires=expires,
             httponly=httponly,
             domain=domain,