diff --git a/addons/mail/static/src/js/discuss.js b/addons/mail/static/src/js/discuss.js
index 76350e0e34f..63885329caf 100644
--- a/addons/mail/static/src/js/discuss.js
+++ b/addons/mail/static/src/js/discuss.js
@@ -196,10 +196,6 @@ 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
      */
     init: function (parent, action, options) {
         this._super.apply(this, arguments);
@@ -223,9 +219,6 @@ 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
@@ -459,7 +452,6 @@ 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 2ec6826b51b..55e6d250600 100644
--- a/addons/mail/static/src/xml/thread.xml
+++ b/addons/mail/static/src/xml/thread.xml
@@ -156,9 +156,6 @@
         @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
 
                      _____________
                     |             |
@@ -172,7 +169,7 @@
 
     -->
     <t t-name="mail.widget.Thread.Content.ASC">
-        <div t-att-class="options.withPhantomJS ? '' : 'o_mail_thread_content_asc'">
+        <div class="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-if="thread.hasTypingNotification()" t-call="mail.widget.Thread.TypingNotificationBar"/>
@@ -186,9 +183,6 @@
         @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
 
                      _____________
                     |             |
@@ -201,7 +195,7 @@
                       DESC Order
     -->
     <t t-name="mail.widget.Thread.Content.DESC">
-        <div t-att-class="options.withPhantomJS ? '' : 'o_mail_thread_content_desc'">
+        <div class="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 6182fd4a5ba..1ea0aab5ae9 100644
--- a/addons/mail/static/tests/discuss_tests.js
+++ b/addons/mail/static/tests/discuss_tests.js
@@ -412,8 +412,7 @@ QUnit.test('older messages are loaded on scroll', function (assert) {
             }
             return this._super.apply(this, arguments);
         },
-    }, { phantomjs: true }) // TODO: remove this option when we no longer use phantomJS
-    .then(function (discuss) {
+    }).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 5e670701494..033866522e6 100644
--- a/addons/mail/static/tests/helpers/test_utils.js
+++ b/addons/mail/static/tests/helpers/test_utils.js
@@ -25,13 +25,9 @@ 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, options) {
+function createDiscuss(params) {
     var Parent = Widget.extend({
         do_push_state: function () {},
     });
@@ -41,7 +37,7 @@ function createDiscuss(params, options) {
             'mail.message,false,search': '<search/>',
         },
     }));
-    var discuss = new Discuss(parent, params, options);
+    var discuss = new Discuss(parent, params);
     discuss.set_cp_bus(new Widget());
     var selector = params.debug ? 'body' : '#qunit-fixture';
     var controlPanel = new ControlPanel(parent);