diff --git a/galatea.py b/galatea.py
index 237b0b9..9963fc4 100644
--- a/galatea.py
+++ b/galatea.py
@@ -86,6 +86,9 @@ class GalateaUser(metaclass=PoolMeta):
         to_save = []
         with Transaction().set_context(context):
             for line in lines:
+                if not line.party:
+                    line.party = user.party
+
                 prices = Product.get_sale_price([line.product], line.quantity or 0)
                 price = prices[line.product.id]
 
@@ -95,6 +98,9 @@ class GalateaUser(metaclass=PoolMeta):
                 else:
                     line.unit_price = price
 
+                # recalculate line data (taxes,...)
+                line.on_change_product()
+
                 to_save.append(line)
 
         if to_save: