diff --git a/account_invoice_tax/wizards/account_invoice_tax.py b/account_invoice_tax/wizards/account_invoice_tax.py
index aac0a08f..c31cd403 100644
--- a/account_invoice_tax/wizards/account_invoice_tax.py
+++ b/account_invoice_tax/wizards/account_invoice_tax.py
@@ -130,13 +130,17 @@ def _get_amount_updated_values(self):
         company_currency = self.invoice_tax_id.move_id.company_currency_id
         not_company_currency = move_currency and move_currency != company_currency
 
-        return {
-            "amount_currency": self.amount if not_company_currency else None,
+        values = {
             "debit": debit_cc if not_company_currency else debit,
             "credit": credit_cc if not_company_currency else credit,
             "balance": (self.amount_company_currency if not_company_currency else self.amount) * (1 if debit else -1),
         }
 
+        if not_company_currency and self.amount:
+            values["amount_currency"] = self.amount
+
+        return values
+
     def _compute_amount_company_currency(self):
         for line in self:
             taxes = line.invoice_tax_id.move_id.tax_totals["subtotals"][0]["tax_groups"]