diff --git a/addons/web/static/src/js/views/basic/basic_model.js b/addons/web/static/src/js/views/basic/basic_model.js
index 4b86e45636e..31fd50ce2bc 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -2053,7 +2053,9 @@ var BasicModel = AbstractModel.extend({
             case 'UPDATE':
                 list._changes.push({operation: 'UPDATE', id: command.id});
                 if (command.data) {
-                    defs.push(this._applyChange(command.id, command.data, { viewType: view.type }));
+                    defs.push(this._applyChange(command.id, command.data, {
+                        viewType: view && view.type,
+                    }));
                 }
                 break;
             case 'FORGET':
diff --git a/addons/web/static/tests/fields/relational_fields/field_one2many_tests.js b/addons/web/static/tests/fields/relational_fields/field_one2many_tests.js
index 425efbee5a9..b4e8c65fd0c 100644
--- a/addons/web/static/tests/fields/relational_fields/field_one2many_tests.js
+++ b/addons/web/static/tests/fields/relational_fields/field_one2many_tests.js
@@ -9764,6 +9764,77 @@ QUnit.module('fields', {}, function () {
 
             form.destroy();
         });
+
+        QUnit.test('update a one2many from a custom field widget', async function (assert) {
+            // In this test, we define a custom field widget to render/update a one2many
+            // field. For the update part, we ensure that updating primitive fields of a sub
+            // record works. There is no guarantee that updating a relational field on the sub
+            // record would work. Deleting a sub record works as well. However, creating sub
+            // records isn't supported. There are obviously a lot of limitations, but the code
+            // hasn't been designed to support all this. This test simply encodes what can be
+            // done, and this comment explains what can't (and won't be implemented in stable
+            // versions).
+            assert.expect(3);
+
+            this.data.partner.records[0].p = [1, 2];
+            const MyRelationalField = AbstractField.extend({
+                events: {
+                    'click .update': '_onUpdate',
+                    'click .delete': '_onDelete',
+                },
+                async _render() {
+                    const records = await this._rpc({
+                        method: 'read',
+                        model: 'partner',
+                        args: [this.value.res_ids],
+                    });
+                    this.$el.text(records.map(r => `${r.display_name}/${r.int_field}`).join(', '));
+                    this.$el.append($('<button class="update fa fa-edit">'));
+                    this.$el.append($('<button class="delete fa fa-trash">'));
+                },
+                _onUpdate() {
+                    this._setValue({
+                        operation: 'UPDATE',
+                        id: this.value.data[0].id,
+                        data: {
+                            display_name: 'new name',
+                            int_field: 44,
+                        },
+                    });
+                },
+                _onDelete() {
+                    this._setValue({
+                        operation: 'DELETE',
+                        ids: [this.value.data[0].id],
+                    });
+                },
+            });
+            fieldRegistry.add('my_relational_field', MyRelationalField);
+
+            const form = await createView({
+                View: FormView,
+                model: 'partner',
+                data: this.data,
+                arch: `
+                    <form>
+                        <field name="p" widget="my_relational_field"/>
+                    </form>`,
+                res_id: 1,
+            });
+
+            assert.strictEqual(form.$('.o_field_widget[name=p]').text(), 'first record/10, second record/9');
+
+            await testUtils.dom.click(form.$('button.update'));
+
+            assert.strictEqual(form.$('.o_field_widget[name=p]').text(), 'new name/44, second record/9');
+
+            await testUtils.dom.click(form.$('button.delete'));
+
+            assert.strictEqual(form.$('.o_field_widget[name=p]').text(), 'second record/9');
+
+            form.destroy();
+            delete fieldRegistry.map.my_relational_field;
+        });
     });
 });
 });