diff --git a/odoo/addons/test_testing_utilities/menu.xml b/odoo/addons/test_testing_utilities/menu.xml
index 60789cb490c..52bdeba2399 100644
--- a/odoo/addons/test_testing_utilities/menu.xml
+++ b/odoo/addons/test_testing_utilities/menu.xml
@@ -164,4 +164,19 @@
             </form>
         </field>
     </record>
+
+    <record id="o2m_modifier" model="ir.ui.view">
+        <field name="name">Modifier check</field>
+        <field name="model">test_testing_utilities.parent</field>
+        <field name="inherit_id" ref="o2m_parent"/>
+        <field name="mode">primary</field>
+        <field name="arch" type="xml">
+            <field name="subs" position="inside">
+                <form>
+                    <field name="value" attrs="{'readonly': [('v', '!=', False)]}"/>
+                    <field name="v"/>
+                </form>
+            </field>
+        </field>
+    </record>
 </odoo>
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 c0e5093fd3b..a7cd141696c 100644
--- a/odoo/addons/test_testing_utilities/tests/test_form_impl.py
+++ b/odoo/addons/test_testing_utilities/tests/test_form_impl.py
@@ -497,6 +497,17 @@ class TestO2M(TransactionCase):
     def test_o2m_self_recursive(self):
         Form(self.env['test_testing_utilities.recursive'], view='test_testing_utilities.o2m_recursive_relation_view')
 
+    def test_o2m_attrs(self):
+        Model = self.env['test_testing_utilities.parent'].with_context(
+            default_subs=[{
+                'value': 5,
+            }, {
+                'value': 7,
+            }]
+        )
+        f = Form(Model, view='test_testing_utilities.o2m_modifier')
+        f.save()
+
 class TestEdition(TransactionCase):
     """ These use the context manager form as we don't need the record
     post-save (we already have it) and it's easier to see what bits act on
diff --git a/odoo/tests/common.py b/odoo/tests/common.py
index 59c4cd334b5..9350ff49327 100644
--- a/odoo/tests/common.py
+++ b/odoo/tests/common.py
@@ -1537,8 +1537,9 @@ class Form(object):
         values = {}
         fields = self._view['fields']
         for f in fields:
+            descr = fields[f]
             v = self._values[f]
-            if self._get_modifier(f, 'required') and not fields[f]['type'] == 'boolean':
+            if self._get_modifier(f, 'required') and not descr['type'] == 'boolean':
                 assert v is not False, "{} is a required field".format(f)
 
             # skip unmodified fields
@@ -1550,8 +1551,8 @@ class Form(object):
                 if not node.get('force_save'):
                     continue
 
-            if fields[f]['type'] == 'one2many':
-                view = fields[f]['views']['edition']
+            if descr['type'] == 'one2many':
+                view = descr['views']['edition']
                 modifiers = view['modifiers']
                 oldvals = v
                 v = []
@@ -1565,7 +1566,21 @@ class Form(object):
                 for (c, rid, vs) in oldvals:
                     if c in (0, 1):
                         items = list(getattr(vs, 'changed_items', vs.items)())
-                        # FIXME: should be more extensive processing of o2m defaults
+                        fields_ = view['fields']
+                        missing = fields_.keys() - vs.keys()
+                        if missing:
+                            Model = self._env[descr['relation']]
+                            if c == 0:
+                                vs.update(dict.fromkeys(missing, False))
+                                vs.update(
+                                    (k, _cleanup_from_default(fields_[k], v))
+                                    for k, v in Model.default_get(list(missing)).items()
+                                )
+                            else:
+                                vs.update(record_to_values(
+                                    {k: v for k, v in fields_.items() if k not in vs},
+                                    Model.browse(rid)
+                                ))
                         vs.setdefault('id', False)
                         vs['•parent•'] = self._values
                         vs = {
@@ -1971,6 +1986,23 @@ def record_to_values(fields, record):
         r[f] = v
     return r
 
+def _cleanup_from_default(type_, value):
+    if not value:
+        if type_ == 'many2many':
+            return [(6, False, [])]
+        elif type_ == 'one2many':
+            return []
+        elif type_ in ('integer', 'float'):
+            return 0
+        return value
+
+    if type_ == 'one2many':
+        return [c for c in value if c[0] != 6]
+    elif type_ == 'datetime' and isinstance(value, datetime):
+        return odoo.fields.Datetime.to_string(value)
+    elif type_ == 'date' and isinstance(value, date):
+        return odoo.fields.Date.to_string(value)
+
 def _get_node(view, f, *arg):
     """ Find etree node for the field ``f`` in the view's arch
     """