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 9af32adda93..11961e6fecf 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -908,7 +908,7 @@ var BasicModel = AbstractModel.extend({
         for (var fieldName in changes) {
             field = record.fields[fieldName];
             if (field.type === 'one2many' || field.type === 'many2many') {
-                defs.push(this._applyX2ManyChange(record, fieldName, changes[fieldName]));
+                defs.push(this._applyX2ManyChange(record, fieldName, changes[fieldName], viewType));
             } else if (field.type === 'many2one') {
                 defs.push(this._applyMany2OneChange(record, fieldName, changes[fieldName]));
             } else {
@@ -1112,13 +1112,15 @@ var BasicModel = AbstractModel.extend({
      * @param {string} fieldName
      * @param {Object} command A command object.  It should have a 'operation'
      *   key.  For example, it looks like {operation: ADD, id: 'partner_1'}
+     * @param {string} [viewType] current viewType. If not set, we will assume
+     *   main viewType from the record
      * @returns {Deferred}
      */
-    _applyX2ManyChange: function (record, fieldName, command) {
+    _applyX2ManyChange: function (record, fieldName, command, viewType) {
         var self = this;
         var list = this.localData[record._changes[fieldName] || record.data[fieldName]];
         var field = record.fields[fieldName];
-        var fieldInfo = record.fieldsInfo[record.viewType][fieldName];
+        var fieldInfo = record.fieldsInfo[viewType || record.viewType][fieldName];
         var view = fieldInfo.views && fieldInfo.views[fieldInfo.mode];
         var rec;
         var defs = [];
@@ -1939,8 +1941,8 @@ var BasicModel = AbstractModel.extend({
                     // generate update commands for records that have been
                     // updated (it may happen with editable lists)
                     _.each(relData, function (relRecord) {
-                        if (!_.isEmpty(relRecord._changes)) {
-                            var changes = self._generateChanges(relRecord);
+                        var changes = self._generateChanges(relRecord);
+                        if (!_.isEmpty(changes)) {
                             var command = x2ManyCommands.update(relRecord.res_id, changes);
                             commands[fieldName].push(command);
                         }
@@ -1958,8 +1960,8 @@ var BasicModel = AbstractModel.extend({
                         if (_.contains(keptIds, relIds[i])) {
                             // this is an id that already existed
                             relRecord = _.findWhere(relData, {res_id: relIds[i]});
-                            if (!_.isEmpty(relRecord._changes)) {
-                                changes = this._generateChanges(relRecord);
+                            changes = this._generateChanges(relRecord);
+                            if (!_.isEmpty(changes)) {
                                 command = x2ManyCommands.update(relRecord.res_id, changes);
                                 didChange = true;
                             } else {
diff --git a/addons/web/static/tests/fields/relational_fields_tests.js b/addons/web/static/tests/fields/relational_fields_tests.js
index 66c825cb3c7..6003cef3d0c 100644
--- a/addons/web/static/tests/fields/relational_fields_tests.js
+++ b/addons/web/static/tests/fields/relational_fields_tests.js
@@ -3103,6 +3103,63 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('one2many with x2many in form view (but not in list view)', function (assert) {
+        assert.expect(1);
+
+        // avoid error when saving the edited related record (because the
+        // related x2m field is unknown in the inline list view)
+        // also ensure that the changes are correctly saved
+
+        this.data.turtle.fields.o2m = {string: "o2m", type: "one2many", relation: 'user'};
+
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form string="Partners">' +
+                    '<group>' +
+                        '<field name="turtles">' +
+                            '<tree>' +
+                                '<field name="turtle_foo"/>' +
+                            '</tree>' +
+                        '</field>' +
+                    '</group>' +
+                '</form>',
+            res_id: 1,
+            archs: {
+                "turtle,false,form": '<form string="Turtles">' +
+                        '<field name="partner_ids" widget="many2many_tags"/>' +
+                    '</form>',
+            },
+            viewOptions: {
+                mode: 'edit',
+            },
+            mockRPC: function (route, args) {
+                if (args.method === 'write') {
+                    assert.deepEqual(args.args[1].turtles, [[1, 2, {
+                        partner_ids: [[6, false, [2, 4, 1]]],
+                    }]]);
+                }
+                return this._super.apply(this, arguments);
+            },
+        });
+
+        form.$('.o_data_row:first').click(); // edit first record
+
+        var $input = $('.modal .o_field_many2manytags input');
+        $input.click(); // opens the dropdown
+        $input.autocomplete('widget').find('li').click(); // add 'first record'
+
+        // add a many2many tag and save
+        $('.modal .o_field_x2many_list_row_add a').click();
+        $('.modal .o_field_widget[name=name]').val('test').trigger('input');
+        $('.modal .modal-footer .btn-primary').click(); // save
+
+        form.$buttons.find('.o_form_button_save').click();
+
+        form.destroy();
+    });
+
     QUnit.test('one2many (who contains display_name) with tree view and without form view', function (assert) {
         assert.expect(1);