diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index abc0694..622b724 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -270,7 +270,7 @@
 		super(SalesInvoice, self).validate()
 		self.validate_auto_set_posting_time()
 
-		if not self.is_pos:
+		if not (self.is_pos or self.is_debit_note):
 			self.so_dn_required()
 
 		self.set_tax_withholding()