diff --git a/erpnext/stock/doctype/stock_entry/stock_entry.py b/erpnext/stock/doctype/stock_entry/stock_entry.py
index f319015..e7e3eb1 100644
--- a/erpnext/stock/doctype/stock_entry/stock_entry.py
+++ b/erpnext/stock/doctype/stock_entry/stock_entry.py
@@ -232,17 +232,16 @@
 						frappe.bold(d.transfer_qty)),
 					NegativeStockError, title=_('Insufficient Stock'))
 
-	def set_serial_nos(self,production_order_id):
-		
-		previous_se = frappe.db.get_value("Stock Entry",{"production_order": production_order_id,
+	def set_serial_nos(self, production_order):
+		previous_se = frappe.db.get_value("Stock Entry", {"production_order": production_order,
 				"purpose": "Material Transfer for Manufacture"}, "name")
 
 		for d in self.get('items'):
-			previous_serial_no = frappe.db.get_value("Stock Entry Detail",{"parent": previous_se,
+			transferred_serial_no = frappe.db.get_value("Stock Entry Detail",{"parent": previous_se,
 				"item_code": d.item_code}, "serial_no")
 			
-			if previous_serial_no:
-				d.serial_no = previous_serial_no
+			if transferred_serial_no:
+				d.serial_no = transferred_serial_no
 
 	def get_stock_and_rate(self):
 		self.set_transfer_qty()