diff --git a/backend/motorsignal_api/app/road_alerts/cache.py b/backend/motorsignal_api/app/road_alerts/cache.py
index 5de6fc7..161c3dc 100644
--- a/backend/motorsignal_api/app/road_alerts/cache.py
+++ b/backend/motorsignal_api/app/road_alerts/cache.py
@@ -308,7 +308,7 @@ class PersistentUsageTracker:
                 stmt = text("""
                     UPDATE provider_monthly_usage
                     SET requests_executed = requests_executed + 1,
-                        estimated_cost_usd = round((requests_executed + 1) * :cost_per_req, 4),
+                        estimated_cost_usd = round(CAST((requests_executed + 1) * :cost_per_req AS numeric), 4),
                         updated_at = :now
                     WHERE provider_id = :provider_id AND period_month = :period
                 """)