diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index d1eddef433f..2be89ab716b 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -3719,6 +3719,7 @@ def update_child_qty_rate(parent_doctype, trans_items, parent_doctype_name, chil
 						).format(frappe.bold(parent.name))
 					)
 	else:  # Sales Order
+		parent.validate_for_duplicate_items()
 		parent.validate_warehouse()
 		parent.update_reserved_qty()
 		parent.update_project()