diff --git a/backend/src/features/vehicles/domain/vehicles.service.ts b/backend/src/features/vehicles/domain/vehicles.service.ts
index a03ebc1..cde91b5 100644
--- a/backend/src/features/vehicles/domain/vehicles.service.ts
+++ b/backend/src/features/vehicles/domain/vehicles.service.ts
@@ -86,11 +86,12 @@ export class VehiclesService {
       await client.query('BEGIN');
 
       // Lock user's vehicle rows and get count
-      const countResult = await client.query(
-        'SELECT COUNT(*) as count FROM vehicles WHERE user_id = $1 AND is_active = true FOR UPDATE',
+      // Note: Cannot use COUNT(*) with FOR UPDATE, so we select IDs and count in app
+      const lockResult = await client.query(
+        'SELECT id FROM vehicles WHERE user_id = $1 AND is_active = true FOR UPDATE',
         [userId]
       );
-      const currentCount = parseInt(countResult.rows[0].count, 10);
+      const currentCount = lockResult.rows.length;
 
       // Check if user can add another vehicle
       if (!canAddVehicle(userTier, currentCount)) {