diff --git a/erpnext/selling/doctype/quotation/quotation.py b/erpnext/selling/doctype/quotation/quotation.py
index d8667f6..8ec2b76 100644
--- a/erpnext/selling/doctype/quotation/quotation.py
+++ b/erpnext/selling/doctype/quotation/quotation.py
@@ -68,13 +68,19 @@
 
 	def declare_enquiry_lost(self, lost_reasons_list, detailed_reason=None):
 		if not self.has_sales_order():
+			get_lost_reasons = frappe.get_list('Opportunity Lost Reason',
+			fields = ["name"])
+			lost_reasons_lst = [reason.get('name') for reason in get_lost_reasons]
 			frappe.db.set(self, 'status', 'Lost')
 
 			if detailed_reason:
 				frappe.db.set(self, 'order_lost_reason', detailed_reason)
 
 			for reason in lost_reasons_list:
-				self.append('lost_reasons', reason)
+				if reason.get('lost_reason') in lost_reasons_lst:
+					self.append('lost_reasons', reason)
+				else:
+					frappe.throw(_("Invalid lost reason <b>{0}</b>, please create a new lost reason".format(reason.get('lost_reason'))))
 
 			self.update_opportunity()
 			self.update_lead()