diff --git a/modules/incoterm/sale.py b/modules/incoterm/sale.py
index 478d597da0..ef0193ba6b 100644
--- a/modules/incoterm/sale.py
+++ b/modules/incoterm/sale.py
@@ -32,8 +32,8 @@ class Sale(IncotermAvailableMixin, metaclass=PoolMeta):
         return shipment
 
     def _get_shipment_grouping_fields(self, shipment):
-        return super()._get_shipment_grouping_fields + (
-            'incoterm', 'incoterm_location')
+        return super()._get_shipment_grouping_fields(shipment) + [
+            'incoterm', 'incoterm_location']
 
     @property
     @fields.depends('company', 'warehouse', 'shipment_address')
diff --git a/modules/sale_invoice_date/sale.py b/modules/sale_invoice_date/sale.py
index b4bdcc70d1..ad4a2c5873 100644
--- a/modules/sale_invoice_date/sale.py
+++ b/modules/sale_invoice_date/sale.py
@@ -129,5 +129,5 @@ class Sale(metaclass=PoolMeta):
         return invoice
 
     def _get_invoice_grouping_fields(self, invoice):
-        return super()._get_invoice_grouping_fields(invoice) + (
-            'invoice_date',)
+        return super()._get_invoice_grouping_fields(invoice) + [
+            'invoice_date']
diff --git a/modules/sale_shipment_cost/sale.py b/modules/sale_shipment_cost/sale.py
index e9fd61e0a7..2ab74f2e52 100644
--- a/modules/sale_shipment_cost/sale.py
+++ b/modules/sale_shipment_cost/sale.py
@@ -357,8 +357,8 @@ class Sale(metaclass=PoolMeta):
         return cost_line
 
     def _get_shipment_grouping_fields(self, shipment):
-        return super()._get_shipment_grouping_fields(shipment) + (
-            'cost_method', 'carrier')
+        return super()._get_shipment_grouping_fields(shipment) + [
+            'cost_method', 'carrier']
 
     @property
     def shipment_cost_amount(self):