diff --git a/src/WMS.Web.Api/Controllers/MaterialController.cs b/src/WMS.Web.Api/Controllers/MaterialController.cs
index 018cb6fe..871bee14 100644
--- a/src/WMS.Web.Api/Controllers/MaterialController.cs
+++ b/src/WMS.Web.Api/Controllers/MaterialController.cs
@@ -19,6 +19,7 @@ using Microsoft.Extensions.Logging;
 using System.Threading.Tasks;
 using System.Collections.Generic;
 using System.Linq;
+using System;
 
 namespace WMS.Web.Api.Controllers
 {