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 e5e7da7867b..4de6ca25187 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -1718,6 +1718,8 @@ var BasicModel = AbstractModel.extend({
             } else if (type === 'many2one' && fieldName in changes) {
                 var value = changes[fieldName];
                 changes[fieldName] = value ? this.localData[value].res_id : false;
+            } else if (changes[fieldName] === null) {
+                changes[fieldName] = false;
             }
         }
         return changes;
@@ -1797,13 +1799,13 @@ var BasicModel = AbstractModel.extend({
                     // the didChange variable keeps track of the fact that at
                     // least one id was updated
                     var didChange = false;
-                    var command, relRecord;
+                    var changes, command, relRecord;
                     for (var i = 0; i < relIds.length; i++) {
                         if (_.contains(keptIds, relIds[i])) {
                             // this is an id that already existed
                             relRecord = _.findWhere(relData, {res_id: relIds[i]});
                             if (!_.isEmpty(relRecord._changes)) {
-                                var changes = this._generateChanges(relRecord);
+                                changes = this._generateChanges(relRecord);
                                 command = x2ManyCommands.update(relRecord.res_id, changes);
                                 didChange = true;
                             } else {
@@ -1813,8 +1815,8 @@ var BasicModel = AbstractModel.extend({
                         } else if (_.contains(addedIds, relIds[i])) {
                             // this is a new id
                             relRecord = _.findWhere(relData, {res_id: relIds[i]});
-                            relRecord = this.get(relRecord.id, {raw: true});
-                            commands[fieldName].push(x2ManyCommands.create(_.omit(relRecord.data, 'id')));
+                            changes = this._generateChanges(relRecord);
+                            commands[fieldName].push(x2ManyCommands.create(changes));
                         }
                     }
                     if (changesOnly && !didChange && addedIds.length === 0 && removedIds.length === 0) {
diff --git a/addons/web/static/tests/views/basic_model_tests.js b/addons/web/static/tests/views/basic_model_tests.js
index 15947103e6e..a81c4a13602 100644
--- a/addons/web/static/tests/views/basic_model_tests.js
+++ b/addons/web/static/tests/views/basic_model_tests.js
@@ -775,6 +775,13 @@ QUnit.module('Views', {
         this.params.res_id = undefined;
         this.params.type = 'record';
 
+        var o2mRecordParams = {
+            fields: this.data.product.fields,
+            fieldNames: ['name'],
+            modelName: 'product',
+            type: 'record',
+        };
+
         var model = createModel({
             Model: BasicModel,
             data: this.data,
@@ -788,18 +795,15 @@ QUnit.module('Views', {
         });
 
         model.load(this.params).then(function (resultID) {
-
             var record = model.get(resultID);
             assert.strictEqual(record.data.product_ids.data.length, 0,
                 "one2many should start with a list of length 0");
 
-            model.makeRecord('product', [{
-                    name: 'name',
-                    string: "Product Name",
-                    type: "char",
-                    value: "xpod"
-                }
-            ]).then(function (relatedRecordID) {
+            // make a default record for the related model
+            model.load(o2mRecordParams).then(function (relatedRecordID) {
+                // update the subrecord
+                model.notifyChanges(relatedRecordID, {name: 'xpod'});
+                // add the subrecord to the o2m of the main record
                 model.notifyChanges(resultID, {
                     product_ids: {operation: "ADD", id: relatedRecordID}
                 });
diff --git a/addons/web/static/tests/views/form_tests.js b/addons/web/static/tests/views/form_tests.js
index 34c65f96914..727db44faa1 100644
--- a/addons/web/static/tests/views/form_tests.js
+++ b/addons/web/static/tests/views/form_tests.js
@@ -2712,5 +2712,46 @@ QUnit.module('Views', {
         form.$buttons.find('.o_form_button_save').click();
         form.destroy();
     });
+
+    QUnit.test('many2manys inside one2manys are saved correctly', function (assert) {
+        assert.expect(1);
+
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form string="Partners">' +
+                    '<sheet>' +
+                        '<field name="p">' +
+                            '<tree editable="top">' +
+                                '<field name="timmy" widget="many2many_tags"/>' +
+                            '</tree>' +
+                        '</field>' +
+                    '</sheet>' +
+                '</form>',
+            mockRPC: function (route, args) {
+                if (args.method === 'create') {
+                    var command = args.args[0].p;
+                    assert.deepEqual(command, [[0, false, {
+                        display_name: false,
+                        timmy: [[6, false, [12]]],
+                    }]], "the default partner_type_id should be equal to 12");
+                }
+                return this._super.apply(this, arguments);
+            },
+        });
+
+        // add a o2m subrecord with a m2m tag
+        form.$('.o_form_field_x2many_list_row_add a').click();
+        form.$('.o_many2many_tags_cell').click();
+        form.$('.o_form_field_many2one input').click();
+        var $dropdown = form.$('.o_form_field_many2one input').autocomplete('widget');
+        $dropdown.find('li:first()').click(); // select the first tag
+
+        form.$buttons.find('.o_form_button_save').click();
+
+        form.destroy();
+    });
+
 });
 });