fix: test_serial_no_case_1 test case works
diff --git a/erpnext/accounts/doctype/pos_invoice_merge_log/pos_invoice_merge_log.py b/erpnext/accounts/doctype/pos_invoice_merge_log/pos_invoice_merge_log.py
index 3a684d4..b587ce6 100644
--- a/erpnext/accounts/doctype/pos_invoice_merge_log/pos_invoice_merge_log.py
+++ b/erpnext/accounts/doctype/pos_invoice_merge_log/pos_invoice_merge_log.py
@@ -389,7 +389,7 @@
 				continue
 
 			return_against_is_added = any(
-				d for d in invoices if d.pos_invoice == pos_invoice.return_against
+				d for d in _invoices if d.pos_invoice == pos_invoice.return_against
 			)
 			if return_against_is_added:
 				break