diff --git a/addons/web/models/models.py b/addons/web/models/models.py
index 6dbc29f6de1..b109bb69686 100644
--- a/addons/web/models/models.py
+++ b/addons/web/models/models.py
@@ -1196,7 +1196,7 @@ class RecordSnapshot(dict):
             commands = []
 
             self_value = self[field_name]
-            other_value = other.get(field_name) or {}
+            other_value = {} if force else other.get(field_name) or {}
             if any(other_value):
                 # other may be a snapshot for a real record, adapt its x2many ids
                 other_value = {NewId(id_): snap for id_, snap in other_value.items()}
diff --git a/odoo/addons/test_testing_utilities/models.py b/odoo/addons/test_testing_utilities/models.py
index 2c6207d0335..b08f306fb20 100644
--- a/odoo/addons/test_testing_utilities/models.py
+++ b/odoo/addons/test_testing_utilities/models.py
@@ -175,13 +175,20 @@ class O2MDefault(models.Model):
     _name = 'test_testing_utilities.default'
     _description = 'Testing Utilities Default'
 
+    value = fields.Integer(default=1)
+    v = fields.Integer()
+    subs = fields.One2many('test_testing_utilities.sub3', 'parent_id', default=lambda self: self._default_subs())
+
     def _default_subs(self):
         return [
             Command.create({'v': 5})
         ]
-    value = fields.Integer(default=1)
-    v = fields.Integer()
-    subs = fields.One2many('test_testing_utilities.sub3', 'parent_id', default=_default_subs)
+
+    @api.onchange('value')
+    def _onchange_value(self):
+        if self.value == 42:
+            self.subs = False
+
 
 class O2MSub3(models.Model):
     _name = 'test_testing_utilities.sub3'
diff --git a/odoo/addons/test_testing_utilities/tests/test_form_impl.py b/odoo/addons/test_testing_utilities/tests/test_form_impl.py
index 277801b0384..237b2e34dce 100644
--- a/odoo/addons/test_testing_utilities/tests/test_form_impl.py
+++ b/odoo/addons/test_testing_utilities/tests/test_form_impl.py
@@ -411,6 +411,12 @@ class TestO2M(TransactionCase):
                 self.assertEqual(s.value, 2)
                 self.assertEqual(s.v, 2, "should have onchanged value to v")
 
+    def test_o2m_default_discarded(self):
+        """ Tests what happens when the default value is discarded. """
+        model = self.env['test_testing_utilities.default']
+        with Form(model.with_context(default_value=42)) as f:
+            self.assertFalse(len(f.subs))
+
     def test_o2m_onchange_parent(self):
         """ Tests that changing o2m content triggers onchange in the parent
         """