diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index c977e736043..bf28f32b30e 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -595,6 +595,9 @@ class SaleOrder(models.Model):
         action['context'] = context
         return action
 
+    def _get_invoice_grouping_keys(self):
+        return ['company_id', 'partner_id', 'currency_id']
+
     def _create_invoices(self, grouped=False, final=False, date=None):
         """
         Create the invoice associated to the SO.
@@ -645,7 +648,8 @@ class SaleOrder(models.Model):
         # 2) Manage 'grouped' parameter: group by (partner_id, currency_id).
         if not grouped:
             new_invoice_vals_list = []
-            for grouping_keys, invoices in groupby(invoice_vals_list, key=lambda x: (x.get('company_id'), x.get('partner_id'), x.get('currency_id'))):
+            invoice_grouping_keys = self._get_invoice_grouping_keys()
+            for grouping_keys, invoices in groupby(invoice_vals_list, key=lambda x: [x.get(grouping_key) for grouping_key in invoice_grouping_keys]):
                 origins = set()
                 payment_refs = set()
                 refs = set()