diff --git a/libs/service/workspace/alert.rs b/libs/service/workspace/alert.rs
index 37852ea..059ae1b 100644
--- a/libs/service/workspace/alert.rs
+++ b/libs/service/workspace/alert.rs
@@ -238,7 +238,7 @@ impl AppService {
         .map(|d| chrono::TimeZone::from_utc_datetime(&chrono::Utc, &d))
         .unwrap_or(now);
 
-        workspace_billing_history::Entity::find()
+        let month_used: f64 = workspace_billing_history::Entity::find()
             .filter(workspace_billing_history::Column::WorkspaceId.eq(workspace_id))
             .filter(workspace_billing_history::Column::Reason.like("ai_usage%"))
             .filter(workspace_billing_history::Column::CreatedAt.gte(month_start))