Correction of amout before tax description (not "Montant HT")

coin/billing/models.py

@@ -161,7 +161,7 @@ class Invoice(models.Model):
         for detail in self.details.all():
             total += detail.amount
         return total.quantize(Decimal('0.01'))
-    amount.short_description = 'Montant HT'
+    amount_before_tax.short_description = 'Montant HT'
 
     def amount_paid(self):
         """