diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index b1cc00fd5b8..e4776634d52 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -505,7 +505,7 @@ class SaleOrder(models.Model):
                 amount = tax.compute_all(line.price_reduce + base_tax, quantity=line.product_uom_qty)['taxes'][0]['amount']
                 res[group] += amount
                 if tax.include_base_amount:
-                    base_tax += amount
+                    base_tax += tax.compute_all(line.price_reduce + base_tax, quantity=1)['taxes'][0]['amount']
         res = sorted(res.items(), key=lambda l: l[0].sequence)
         res = map(lambda l: (l[0].name, l[1]), res)
         return res