diff --git a/addons/account/models/account_move.py b/addons/account/models/account_move.py
index aa40757ff2b..326af6d2e00 100644
--- a/addons/account/models/account_move.py
+++ b/addons/account/models/account_move.py
@@ -2857,8 +2857,12 @@ class AccountMoveLine(models.Model):
                 'discount': 0.0,
                 'price_unit': balance / (quantity or 1.0),
             }
-        else:
+        elif not discount_factor:
+            # balance of line is 0, but discount  == 100% so we display the normal unit_price
             vals = {}
+        else:
+            # balance is 0, so unit price is 0 as well
+            vals = {'price_unit': 0.0}
         return vals
 
     # -------------------------------------------------------------------------
diff --git a/addons/account/tests/test_account_move_in_invoice.py b/addons/account/tests/test_account_move_in_invoice.py
index 324f75b844a..a1e9b0f9ad1 100644
--- a/addons/account/tests/test_account_move_in_invoice.py
+++ b/addons/account/tests/test_account_move_in_invoice.py
@@ -477,8 +477,8 @@ class TestAccountMoveInInvoiceOnchanges(AccountTestInvoicingCommon):
     def test_in_invoice_line_onchange_business_fields_1(self):
         move_form = Form(self.invoice)
         with move_form.invoice_line_ids.edit(0) as line_form:
-            # Current price_unit is 1000.
-            # We set quantity = 4, discount = 50%, price_unit = 400 because (4 * 400) * 0.5 = 800.
+            # Current price_unit is 800.
+            # We set quantity = 4, discount = 50%, price_unit = 400. The debit/credit fields don't change because (4 * 400) * 0.5 = 800.
             line_form.quantity = 4
             line_form.discount = 50
             line_form.price_unit = 400
diff --git a/addons/account/tests/test_account_move_in_refund.py b/addons/account/tests/test_account_move_in_refund.py
index 897ee41b4be..7c3c600ce3d 100644
--- a/addons/account/tests/test_account_move_in_refund.py
+++ b/addons/account/tests/test_account_move_in_refund.py
@@ -189,8 +189,8 @@ class TestAccountMoveInRefundOnchanges(AccountTestInvoicingCommon):
     def test_in_refund_line_onchange_business_fields_1(self):
         move_form = Form(self.invoice)
         with move_form.invoice_line_ids.edit(0) as line_form:
-            # Current price_unit is 1000.
-            # We set quantity = 4, discount = 50%, price_unit = 400 because (4 * 400) * 0.5 = 800.
+            # Current price_unit is 800.
+            # We set quantity = 4, discount = 50%, price_unit = 400. The debit/credit fields don't change because (4 * 400) * 0.5 = 800.
             line_form.quantity = 4
             line_form.discount = 50
             line_form.price_unit = 400
diff --git a/addons/account/tests/test_account_move_out_invoice.py b/addons/account/tests/test_account_move_out_invoice.py
index 2eb0b43a2da..524da8697f3 100644
--- a/addons/account/tests/test_account_move_out_invoice.py
+++ b/addons/account/tests/test_account_move_out_invoice.py
@@ -480,7 +480,7 @@ class TestAccountMoveOutInvoiceOnchanges(AccountTestInvoicingCommon):
         move_form = Form(self.invoice)
         with move_form.invoice_line_ids.edit(0) as line_form:
             # Current price_unit is 1000.
-            # We set quantity = 4, discount = 50%, price_unit = 500 because (4 * 500) * 0.5 = 1000.
+            # We set quantity = 4, discount = 50%, price_unit = 400. The debit/credit fields don't change because (4 * 500) * 0.5 = 1000.
             line_form.quantity = 4
             line_form.discount = 50
             line_form.price_unit = 500
diff --git a/addons/account/tests/test_account_move_out_refund.py b/addons/account/tests/test_account_move_out_refund.py
index e7f7a66df37..8f9e9c0da8b 100644
--- a/addons/account/tests/test_account_move_out_refund.py
+++ b/addons/account/tests/test_account_move_out_refund.py
@@ -190,7 +190,7 @@ class TestAccountMoveOutRefundOnchanges(AccountTestInvoicingCommon):
         move_form = Form(self.invoice)
         with move_form.invoice_line_ids.edit(0) as line_form:
             # Current price_unit is 1000.
-            # We set quantity = 4, discount = 50%, price_unit = 500 because (4 * 500) * 0.5 = 1000.
+            # We set quantity = 4, discount = 50%, price_unit = 400. The debit/credit fields don't change because (4 * 500) * 0.5 = 1000.
             line_form.quantity = 4
             line_form.discount = 50
             line_form.price_unit = 500