diff -r 6597f33e51d2 invoice.py
--- a/trytond/trytond/modules/account_invoice/invoice.py	Fri Aug 09 16:33:39 2019 +0200
+++ b/trytond/trytond/modules/account_invoice/invoice.py	Wed Aug 28 23:44:50 2019 +0200
@@ -2267,7 +2267,7 @@
         else:
             self.account = tax.credit_note_account
 
-    @fields.depends('tax', 'base', 'amount', 'manual', 'invoice',
+    @fields.depends('tax', 'base', 'manual', 'invoice',
         '_parent_invoice.currency')
     def on_change_with_amount(self):
         Tax = Pool().get('account.tax')
@@ -2281,7 +2281,6 @@
                     if self.invoice.currency:
                         amount = self.invoice.currency.round(amount)
                     return amount
-        return self.amount
 
     @classmethod
     def check_modify(cls, taxes):