diff --git a/erpnext/accounts/report/payment_period_based_on_invoice_date/payment_period_based_on_invoice_date.py b/erpnext/accounts/report/payment_period_based_on_invoice_date/payment_period_based_on_invoice_date.py
index 604bc56..786a494 100644
--- a/erpnext/accounts/report/payment_period_based_on_invoice_date/payment_period_based_on_invoice_date.py
+++ b/erpnext/accounts/report/payment_period_based_on_invoice_date/payment_period_based_on_invoice_date.py
@@ -18,7 +18,7 @@
 
 	data = []
 	for d in entries:
-		against_date = invoice_posting_date_map[d.reference_name] or ""
+		against_date = invoice_posting_date_map.get(d.reference_name) or ""
 		if d.reference_type=="Purchase Invoice":
 			payment_amount = flt(d.debit) or -1 * flt(d.credit)
 		else: