Added validation for update items in purchase order as well
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 56ae25e..fe6b39d 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -1074,9 +1074,12 @@
 	for d in data:
 		child_item = frappe.get_doc(parent_doctype + ' Item', d.get("docname"))
 
-		if flt(d.get("qty")) < child_item.delivered_qty:
+		if parent_doctype == "Sales Order" and flt(d.get("qty")) < child_item.delivered_qty:
 			frappe.throw(_("Cannot set quantity less than delivered quantity"))
 
+		if parent_doctype == "Purchase Order" and flt(d.get("qty")) < child_item.received_qty:
+			frappe.throw(_("Cannot set quantity less than received quantity"))
+
 		child_item.qty = flt(d.get("qty"))
 
 		if child_item.billed_amt > (flt(d.get("rate")) * flt(d.get("qty"))):