diff --git a/app/db/crud.py b/app/db/crud.py
index 1f7272e..dc10aa1 100644
--- a/app/db/crud.py
+++ b/app/db/crud.py
@@ -725,12 +725,15 @@ def revoke_user_sub(db: Session, dbuser: User):
 
 
 def update_user_sub(db: Session, dbuser: User, user_agent: str):
-    dbuser.sub_updated_at = datetime.utcnow()
-    dbuser.sub_last_user_agent = user_agent
-
-    db.commit()
-    db.refresh(dbuser)
-    return dbuser
+    with db.get_bind().begin() as conn:
+        conn.execute(
+            update(User)
+            .where(User.id == dbuser.id)
+            .values(
+                sub_updated_at=datetime.utcnow(),
+                sub_last_user_agent=user_agent,
+            )
+        )
 
 
 def reset_all_users_data_usage(db: Session, admin: Optional[Admin] = None):
diff --git a/app/models/user.py b/app/models/user.py
index c03b728..34938c1 100644
--- a/app/models/user.py
+++ b/app/models/user.py
@@ -40,9 +40,16 @@ class User(BaseModel):
     ]
     expire_strategy: UserExpireStrategy
     expire_date: datetime | None = Field(None)
-    usage_duration: Annotated[
-        int, Field(le=9999 * 365 * 24 * 60 * 60, description="usage_duration must be less than 9999 years")
-    ] | None = None, 
+    usage_duration: (
+        Annotated[
+            int,
+            Field(
+                le=9999 * 365 * 24 * 60 * 60,
+                description="usage_duration must be less than 9999 years",
+            ),
+        ]
+        | None
+    ) = (None,)
     activation_deadline: datetime | None = Field(None)
     key: str = Field(default_factory=lambda: secrets.token_hex(16))
     data_limit: int | None = Field(