diff --git a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
index 7b2061a..917acba 100644
--- a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
+++ b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
@@ -248,7 +248,7 @@
 	def set_against_expense_account(self):
 		against_accounts = []
 		for item in self.get("items"):
-			if item.expense_account not in against_accounts:
+			if item.expense_account and (item.expense_account not in against_accounts):
 				against_accounts.append(item.expense_account)
 
 		self.against_expense_account = ",".join(against_accounts)