diff --git a/addons/mail/static/src/js/form_renderer.js b/addons/mail/static/src/js/form_renderer.js
index 520827d7695..9d9532e2171 100644
--- a/addons/mail/static/src/js/form_renderer.js
+++ b/addons/mail/static/src/js/form_renderer.js
@@ -1,7 +1,9 @@
 odoo.define('mail.form_renderer', function (require) {
 "use strict";
 
+var BasicModel = require('web.BasicModel');
 var Chatter = require('mail.Chatter');
+var FormController = require('web.FormController');
 var FormRenderer = require('web.FormRenderer');
 
 /**
@@ -88,4 +90,51 @@ FormRenderer.include({
     },
 });
 
+/**
+ * Include the FormController and BasicModel to update the datapoint on the
+ * model when a message is posted.
+ */
+FormController.include({
+    custom_events: _.extend({}, FormController.prototype.custom_events, {
+        new_message: '_onNewMessage',
+    }),
+
+    //--------------------------------------------------------------------------
+    // Handlers
+    //--------------------------------------------------------------------------
+
+    /**
+     * @private
+     * @param {OdooEvent} event
+     * @param {string} event.data.id datapointID
+     * @param {integer[]} event.data.msgIDs list of message ids
+     */
+    _onNewMessage: function (event) {
+        this.model.updateMessageIDs(event.data.id, event.data.msgIDs);
+    },
+});
+
+BasicModel.include({
+
+    //--------------------------------------------------------------------------
+    // Public
+    //--------------------------------------------------------------------------
+
+    /**
+     * Update the message ids on a datapoint.
+     *
+     * Note that we directly update the res_ids on the datapoint as the message
+     * has already been posted ; this change can't be handled 'normally' with
+     * x2m commands because the change won't be saved as a normal field.
+     *
+     * @param {string} id
+     * @param {integer[]} msgIDs
+     */
+    updateMessageIDs: function (id, msgIDs) {
+        var element = this.localData[id];
+        element.res_ids = msgIDs;
+        element.count = msgIDs.length;
+    },
+});
+
 });
diff --git a/addons/mail/static/src/js/thread_field.js b/addons/mail/static/src/js/thread_field.js
index 0d7635cae8b..75e379e6ea1 100644
--- a/addons/mail/static/src/js/thread_field.js
+++ b/addons/mail/static/src/js/thread_field.js
@@ -107,6 +107,10 @@ var ThreadField = AbstractField.extend(chat_mixin, {
     _onNewMessage: function (message) {
         if (message.model === this.model && message.res_id === this.res_id) {
             this.msgIDs.unshift(message.id);
+            this.trigger_up('new_message', {
+                id: this.value.id,
+                msgIDs: this.msgIDs,
+            });
             this._fetchAndRenderThread(this.msgIDs);
         }
     },
diff --git a/addons/mail/static/tests/chatter_tests.js b/addons/mail/static/tests/chatter_tests.js
index c650f8c10c9..409b729fc78 100644
--- a/addons/mail/static/tests/chatter_tests.js
+++ b/addons/mail/static/tests/chatter_tests.js
@@ -494,6 +494,86 @@ QUnit.test('chatter: post, receive and star messages', function (assert) {
         });
 });
 
+
+QUnit.test('chatter: post a message and switch in edit mode', function (assert) {
+    assert.expect(5);
+
+    var messages = [];
+    var bus = new Bus();
+    var form = createView({
+        View: FormView,
+        model: 'partner',
+        data: this.data,
+        arch: '<form string="Partners">' +
+                '<sheet>' +
+                    '<field name="foo"/>' +
+                '</sheet>' +
+                '<div class="oe_chatter">' +
+                    '<field name="message_ids" widget="mail_thread" options="{\'display_log_button\': True}"/>' +
+                '</div>' +
+            '</form>',
+        res_id: 2,
+        session: {},
+        mockRPC: function (route, args) {
+            if (route === "/web/dataset/call_kw/partner/message_get_suggested_recipients") {
+                return $.when({2: []});
+            }
+            return this._super(route, args);
+        },
+        intercepts: {
+            get_messages: function (event) {
+                event.stopPropagation();
+                var requested_msgs = _.filter(messages, function (msg) {
+                    return _.contains(event.data.options.ids, msg.id);
+                });
+                event.data.callback($.when(requested_msgs));
+            },
+            post_message: function (event) {
+                event.stopPropagation();
+                messages.push({
+                    attachment_ids: [],
+                    author_id: ["42", "Me"],
+                    body: event.data.message.content,
+                    date: moment(), // now
+                    displayed_author: "Me",
+                    id: 42,
+                    is_note: event.data.message.subtype === 'mail.mt_note',
+                    is_starred: false,
+                    model: 'partner',
+                    res_id: 2,
+                });
+                bus.trigger('new_message', {
+                    id: 42,
+                    model: event.data.options.model,
+                    res_id: event.data.options.res_id,
+                });
+            },
+            get_bus: function (event) {
+                event.stopPropagation();
+                event.data.callback(bus);
+            },
+        },
+    });
+
+    assert.strictEqual(form.$('.o_thread_message').length, 0, "thread should not contain messages");
+
+    // send a message
+    form.$('.o_chatter_button_new_message').click();
+    form.$('.oe_chatter .o_composer_text_field:first()').val("My first message");
+    form.$('.oe_chatter .o_composer_button_send').click();
+    assert.strictEqual(form.$('.o_thread_message').length, 1, "thread should contain a message");
+    assert.ok(form.$('.o_thread_message:first() .o_thread_message_core').text().indexOf('My first message') >= 0,
+        "the message's body should be correct");
+
+    // switch in edit mode
+    form.$buttons.find('.o_form_button_edit').click();
+    assert.strictEqual(form.$('.o_thread_message').length, 1, "thread should contain a message");
+    assert.ok(form.$('.o_thread_message:first() .o_thread_message_core').text().indexOf('My first message') >= 0,
+        "the message's body should be correct");
+
+    form.destroy();
+});
+
 QUnit.test('form activity widget: schedule next activity', function (assert) {
     assert.expect(5);
     this.data.partner.records[0].activity_ids = [1];