diff --git a/addons/mail/static/src/js/discuss.js b/addons/mail/static/src/js/discuss.js
index d3ed2b06a1d..ede167aa6a5 100644
--- a/addons/mail/static/src/js/discuss.js
+++ b/addons/mail/static/src/js/discuss.js
@@ -196,10 +196,10 @@ var Discuss = AbstractAction.extend(ControlPanelMixin, {
     /**
      * @override
      * @param {Object} [options]
-    //  * @param {boolean} [options.phantomjs=false] if set, rendering of non-empty
-    //  *   thread will use 'block' display instead of 'flex', because phantomjs
-    //  *   sucks with flexbox... TODO: remove this option when we no longer use
-    //  *   phantomJS
+     * @param {boolean} [options.phantomjs=false] if set, rendering of non-empty
+     *   thread will use 'block' display instead of 'flex', because phantomjs
+     *   sucks with flexbox... TODO: remove this option when we no longer use
+     *   phantomJS
      */
     init: function (parent, action, options) {
         this._super.apply(this, arguments);
@@ -223,6 +223,9 @@ var Discuss = AbstractAction.extend(ControlPanelMixin, {
         this._selectedMessage = null;
         this._throttledUpdateThreads = _.throttle(
             this._updateThreads.bind(this), 100, { leading: false });
+
+        // TODO: remove this option when we no longer use phantomJS
+        this._withPhantomJS = this.options.phantomjs || false;
     },
     /**
      * @override
@@ -456,6 +459,7 @@ var Discuss = AbstractAction.extend(ControlPanelMixin, {
             displayEmailIcons: false,
             displayReplyIcons: true,
             displayBottomThreadFreeSpace: true,
+            withPhantomJS: this._withPhantomJS, // TODO: remove this option when we no longer use phantomJS
         };
     },
     /**
diff --git a/addons/mail/static/src/xml/thread.xml b/addons/mail/static/src/xml/thread.xml
index b33452382ac..9b81e5e8d28 100644
--- a/addons/mail/static/src/xml/thread.xml
+++ b/addons/mail/static/src/xml/thread.xml
@@ -156,6 +156,9 @@
         @param {boolean} [options.displayLoadMore=false]
         @param {string|integer} [options.messagesSeparatorPosition] 'top' or
             message ID, the separator is placed just after this message.
+        @param {boolean} [options.withPhantomJS=false] phantomJS is a mess with flexbox
+            so it may break some features like auto-fetch message on scroll.
+            TODO: remove this option when we no longer use phantomJS
 
                      _____________
                     |             |
@@ -169,7 +172,7 @@
 
     -->
     <t t-name="mail.widget.Thread.Content.ASC">
-        <div class="o_mail_thread_content_asc">
+        <div t-att-class="options.withPhantomJS ? '' : 'o_mail_thread_content_asc'">
             <t t-if="options.messagesSeparatorPosition == 'top'" t-call="mail.MessagesSeparator"/>
             <t t-set="messages" t-value="messages.slice().reverse()"/>
             <t t-call="mail.widget.Thread.Messages"/>
@@ -182,6 +185,9 @@
         @param {Object} options
         @param {boolean} [options.displayBottomThreadFreeSpace=false]
         @param {boolean} [options.displayLoadMore=false]
+        @param {boolean} [options.withPhantomJS=false] phantomJS is a mess with flexbox
+            so it may break some features like auto-fetch message on scroll.
+            TODO: remove this option when we no longer use phantomJS
 
                      _____________
                     |             |
@@ -194,7 +200,7 @@
                       DESC Order
     -->
     <t t-name="mail.widget.Thread.Content.DESC">
-        <div class="o_mail_thread_content_desc">
+        <div t-att-class="options.withPhantomJS ? '' : 'o_mail_thread_content_desc'">
             <t t-if="options.displayLoadMore" t-call="mail.widget.Thread.LoadMore"/>
             <t t-call="mail.widget.Thread.Messages"/>
             <t t-if="options.displayBottomThreadFreeSpace">
diff --git a/addons/mail/static/tests/discuss_tests.js b/addons/mail/static/tests/discuss_tests.js
index 6f605d24680..4129911e654 100644
--- a/addons/mail/static/tests/discuss_tests.js
+++ b/addons/mail/static/tests/discuss_tests.js
@@ -406,7 +406,8 @@ QUnit.test('older messages are loaded on scroll', function (assert) {
             }
             return this._super.apply(this, arguments);
         },
-    }).then(function (discuss) {
+    }, { phantomjs: true }) // TODO: remove this option when we no longer use phantomJS
+    .then(function (discuss) {
 
         assert.verifySteps(['message_fetch'],
             "should fetch messages once for needaction messages (Inbox)");
diff --git a/addons/mail/static/tests/helpers/test_utils.js b/addons/mail/static/tests/helpers/test_utils.js
index 033866522e6..5e670701494 100644
--- a/addons/mail/static/tests/helpers/test_utils.js
+++ b/addons/mail/static/tests/helpers/test_utils.js
@@ -25,9 +25,13 @@ var Widget = require('web.Widget');
  * This is async due to mail_manager/mail_service that needs to be ready.
  *
  * @param {Object} params
+ * @param {Object} options
+ * @param {boolean} options.phantomjs if set, rendering of non-empty thread will
+ *   use 'block' display instead of 'flex', because phantomjs sucks with flexbox
+ *   TODO: remove this option when we no longer use phantomJS
  * @return {$.Promise} resolved with the discuss widget
  */
-function createDiscuss(params) {
+function createDiscuss(params, options) {
     var Parent = Widget.extend({
         do_push_state: function () {},
     });
@@ -37,7 +41,7 @@ function createDiscuss(params) {
             'mail.message,false,search': '<search/>',
         },
     }));
-    var discuss = new Discuss(parent, params);
+    var discuss = new Discuss(parent, params, options);
     discuss.set_cp_bus(new Widget());
     var selector = params.debug ? 'body' : '#qunit-fixture';
     var controlPanel = new ControlPanel(parent);