diff --git a/modules/account_invoice/invoice.py b/modules/account_invoice/invoice.py
index 26652ca..8dd20a0 100755
--- a/modules/account_invoice/invoice.py
+++ b/modules/account_invoice/invoice.py
@@ -1288,14 +1288,16 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
         remainder = sum(l.debit - l.credit for l in move_lines)
         if self.payment_term:
             payment_date = self.payment_term_date or self.invoice_date or today
-            model = str(self.lines[0].origin).split(",")[0] if self.lines[0].origin else None
+            origin = self.lines[0].origin if self.lines and self.lines[0].origin else None
+            model = str(origin).split(",")[0] if origin else None
             logger.info("MODEL:%s",model)
+            line = None
             if model:
                 Line = Pool().get(model)
-                line = Line(int(str(self.lines[0].origin).split(",")[1]))
+                line = Line(int(str(origin).split(",")[1]))
                 logger.info("LINE:%s",line)
-                term_lines = self.payment_term.compute(
-                    self.total_amount, self.currency, payment_date, line)
+            term_lines = self.payment_term.compute(
+                self.total_amount, self.currency, payment_date, line)
         else:
             term_lines = [(self.payment_term_date or today, self.total_amount)]
         past_payment_term_dates = []