diff --git a/addons/account/account_invoice.py b/addons/account/account_invoice.py
index a9b181e2555..7fc83b4e42a 100644
--- a/addons/account/account_invoice.py
+++ b/addons/account/account_invoice.py
@@ -1533,7 +1533,7 @@ class account_invoice_tax(models.Model):
             currency = self.env['res.currency'].browse(currency_id)
             currency = currency.with_context(date=date_invoice or fields.Date.context_today(self))
             amount = currency.compute(amount, company.currency_id, round=False)
-        tax_sign = self.tax_amount/self.amount
+        tax_sign = (self.tax_amount / self.amount) if self.amount else 1
         return {'value': {'tax_amount': amount * tax_sign}}
 
     @api.v8