diff --git a/folio.py b/folio.py
index f01ccfe..887e50e 100644
--- a/folio.py
+++ b/folio.py
@@ -1750,11 +1750,11 @@ class FolioCharge(Workflow, ModelSQL, ModelView):
     def set_unit_price_w_tax(cls, charges, name, value):
         Tax = Pool().get('account.tax')
         to_write = []
-        rvalue = Decimal(value).quantize('0.01')
+        rvalue = Decimal(value).quantize(Decimal('0.01'))
         for charge in charges:
             taxes = charge.product.customer_taxes_used
             unit_price = Tax.reverse_compute(rvalue, taxes)
-            unit_price = Decimal(unit_price).quantize('0.01')
+            unit_price = Decimal(unit_price).quantize(Decimal('0.01'))
             to_write.extend([[charge], {
                 'unit_price': unit_price,
             }])