diff --git a/tax.py b/tax.py
index 9ad8a02fb2..7c217b2d4f 100644
--- a/tax.py
+++ b/tax.py
@@ -1082,7 +1082,7 @@ class TaxableMixin(object):
             taxable_lines = [_TaxableLine(*params)
                 for params in self.taxable_lines]
             for line in taxable_lines:
-                l_taxes = Tax.compute(line.taxes, line.unit_price,
+                l_taxes = Tax.compute(Tax.browse(line.taxes), line.unit_price,
                     line.quantity, self.tax_date)
                 for tax in l_taxes:
                     taxline = self._compute_tax_line(**tax)