diff --git a/src/WMS.Web.Repositories/SerialNumbersRepositories.cs b/src/WMS.Web.Repositories/SerialNumbersRepositories.cs
index 954c59cd..2d169fdc 100644
--- a/src/WMS.Web.Repositories/SerialNumbersRepositories.cs
+++ b/src/WMS.Web.Repositories/SerialNumbersRepositories.cs
@@ -153,7 +153,7 @@ namespace WMS.Web.Repositories
                 .GroupJoin(_context.BoxInventory, serial => serial.BoxId, box => box.BoxId, (serial, box) => new { serial, box })
                 .SelectMany(x => x.box.DefaultIfEmpty(), (p, box) => new { p.serial, box })
                 .FirstOrDefaultAsync(w => serialNumber.Equals(w.serial.SerialNumber));
-            if (entity.serial == null) return null;
+            if (entity == null || entity.serial == null) return null;
             response.BoxId = entity.serial.BoxId;
             response.SubStockId = entity.box?.SubStockId ?? 0;
             response.SerialNumber = entity.serial.SerialNumber;