fix: can't compare datetime.date to unicode
diff --git a/erpnext/selling/doctype/quotation/quotation.py b/erpnext/selling/doctype/quotation/quotation.py
index cc73e76..46009f4 100644
--- a/erpnext/selling/doctype/quotation/quotation.py
+++ b/erpnext/selling/doctype/quotation/quotation.py
@@ -34,7 +34,7 @@
 			self.with_items = 1
 
 	def validate_valid_till(self):
-		if self.valid_till and self.valid_till < self.transaction_date:
+		if self.valid_till and getdate(self.valid_till) < getdate(self.transaction_date):
 			frappe.throw(_("Valid till date cannot be before transaction date"))
 
 	def has_sales_order(self):