diff --git a/WarehouseMgr/Tnb.WarehouseMgr/WmsPrdInstockHService.cs b/WarehouseMgr/Tnb.WarehouseMgr/WmsPrdInstockHService.cs
index ebfe6278..b3076bb0 100644
--- a/WarehouseMgr/Tnb.WarehouseMgr/WmsPrdInstockHService.cs
+++ b/WarehouseMgr/Tnb.WarehouseMgr/WmsPrdInstockHService.cs
@@ -392,7 +392,7 @@ namespace Tnb.WarehouseMgr
                 erpRequestData.Add("dbilldate", nowStr);
                 erpRequestData.Add("dmakedate", nowStr);
                 erpRequestData.Add("fbillflag", 1);
-                erpRequestData.Add("ntotalnum", allInstockDetails.Sum(x=>x.pqty));
+                erpRequestData.Add("ntotalnum", allInstockDetails!=null ? allInstockDetails.Sum(x=>x.pqty) : 0);
                 erpRequestData.Add("pk_org", erpOrg.pk_org);
                 erpRequestData.Add("pk_org_v", erpOrg.pk_org_v);
                 erpRequestData.Add("pk_group", erpOrg.pk_group);