diff --git a/www/addons/mod_forum/controllers/discussion.js b/www/addons/mod_forum/controllers/discussion.js
index 388f5e82f3a..81ae46aef59 100644
--- a/www/addons/mod_forum/controllers/discussion.js
+++ b/www/addons/mod_forum/controllers/discussion.js
@@ -21,12 +21,12 @@ angular.module('mm.addons.mod_forum')
  * @ngdoc controller
  * @name mmaModForumDiscussionCtrl
  */
-.controller('mmaModForumDiscussionCtrl', function($q, $scope, $stateParams, $mmaModForum, $mmSite, $mmUtil, $ionicScrollDelegate,
-            mmaModForumComponent) {
+.controller('mmaModForumDiscussionCtrl', function($q, $scope, $stateParams, $mmaModForum, $mmSite, $mmUtil, $translate,
+            $ionicScrollDelegate, mmaModForumComponent) {
 
     var discussionid = $stateParams.discussionid,
         courseid = $stateParams.courseid,
-        scrollView = $ionicScrollDelegate.$getByHandle('mmaModForumPostsScroll');
+        scrollView;
 
     $scope.component = mmaModForumComponent;
     $scope.courseid = courseid;
@@ -41,6 +41,12 @@ angular.module('mm.addons.mod_forum')
         return $mmaModForum.getDiscussionPosts(discussionid).then(function(posts) {
             $scope.discussion = $mmaModForum.extractStartingPost(posts);
             $scope.posts = posts;
+
+            // Set default reply subject.
+            return $translate('mma.mod_forum.re').then(function(strReplyPrefix) {
+                $scope.defaultSubject = strReplyPrefix + ' ' + $scope.discussion.subject;
+                $scope.newpost.subject = $scope.defaultSubject;
+            });
         }, function(message) {
             $mmUtil.showErrorModal(message);
             return $q.reject();
@@ -72,10 +78,13 @@ angular.module('mm.addons.mod_forum')
 
     // New post added.
     $scope.newPostAdded = function() {
-        scrollView.scrollTop();
+        if (!scrollView) {
+            scrollView = $ionicScrollDelegate.$getByHandle('mmaModForumPostsScroll');
+        }
+        scrollView && scrollView.scrollTop && scrollView.scrollTop();
 
         $scope.newpost.replyingto = undefined;
-        $scope.newpost.subject = '';
+        $scope.newpost.subject = $scope.defaultSubject;
         $scope.newpost.message = '';
 
         $scope.discussionLoaded = false;
diff --git a/www/addons/mod_forum/directives/discussionpost.js b/www/addons/mod_forum/directives/discussionpost.js
index 3812305ec3f..e0ce7fe3841 100644
--- a/www/addons/mod_forum/directives/discussionpost.js
+++ b/www/addons/mod_forum/directives/discussionpost.js
@@ -20,6 +20,19 @@ angular.module('mm.addons.mod_forum')
  * @module mm.addons.mod_forum
  * @ngdoc directive
  * @name mmaForumDiscussionPost
+ * @description
+ * This directive will show a forum post if the right data is supplied. Attributes:
+ *
+ * @param {Object} post             Post.
+ * @param {Number} courseid         Post's course ID.
+ * @param {String} title            Post's title.
+ * @param {String} subject          Post's subject.
+ * @param {String} component        Component this post belong to.
+ * @param {Object} newpost          Object with the new post data. Usually shared between posts.
+ * @param {Boolean} showdivider     True if it should have a list divider before the post.
+ * @param {Boolean} titleimportant  True if title should be "important" (bold).
+ * @oaram {Function} [postadded]    Function to call when a new post is added.
+ * @param {String} [defaultsubject] Default subject to set to new posts.
  */
 .directive('mmaModForumDiscussionPost', function($mmaModForum, $mmUtil, $translate, $q) {
     return {
@@ -33,7 +46,8 @@ angular.module('mm.addons.mod_forum')
             newpost: '=',
             showdivider: '=?',
             titleimportant: '=?',
-            postadded: '&?'
+            postadded: '&?',
+            defaultsubject: '=?'
         },
         templateUrl: 'addons/mod_forum/templates/discussionpost.html',
         transclude: true,
@@ -85,7 +99,7 @@ angular.module('mm.addons.mod_forum')
 
                 promise.then(function() {
                     scope.newpost.replyingto = undefined;
-                    scope.newpost.subject = '';
+                    scope.newpost.subject = scope.defaultsubject || '';
                     scope.newpost.message = '';
                 });
             };
diff --git a/www/addons/mod_forum/lang/en.json b/www/addons/mod_forum/lang/en.json
index 5b76d919d50..10084c7dc29 100644
--- a/www/addons/mod_forum/lang/en.json
+++ b/www/addons/mod_forum/lang/en.json
@@ -15,6 +15,7 @@
     "numdiscussions": "{{numdiscussions}} discussions",
     "numreplies": "{{numreplies}} replies",
     "posttoforum": "Post to forum",
+    "re": "Re:",
     "reply": "Reply",
     "subject": "Subject"
 }
diff --git a/www/addons/mod_forum/templates/discussion.html b/www/addons/mod_forum/templates/discussion.html
index efcd09c646c..d8cbd2a4b73 100644
--- a/www/addons/mod_forum/templates/discussion.html
+++ b/www/addons/mod_forum/templates/discussion.html
@@ -6,11 +6,11 @@
         </ion-refresher>
         <mm-loading hide-until="discussionLoaded">
             <article class="card" ng-if="discussion">
-                <mma-mod-forum-discussion-post post="discussion" courseid="courseid" title="discussion.subject" subject="discussion.userfullname" component="component" newpost="newpost" replyingto="replyingto" showdivider="false" titleimportant="true" postadded="newPostAdded()"></mma-mod-forum-discussion-post>
+                <mma-mod-forum-discussion-post post="discussion" courseid="courseid" title="discussion.subject" subject="discussion.userfullname" component="component" newpost="newpost" replyingto="replyingto" showdivider="false" titleimportant="true" postadded="newPostAdded()" defaultsubject="defaultSubject"></mma-mod-forum-discussion-post>
             </article>
             <div class="card" ng-if="posts && posts.length">
                 <article ng-repeat="post in posts track by $index">
-                    <mma-mod-forum-discussion-post post="post" courseid="courseid" title="post.userfullname" subject="post.subject" component="component" newpost="newpost" replyingto="replyingto" showdivider="$index > 0" titleimportant="false" postadded="newPostAdded()"></mma-mod-forum-discussion-post>
+                    <mma-mod-forum-discussion-post post="post" courseid="courseid" title="post.userfullname" subject="post.subject" component="component" newpost="newpost" replyingto="replyingto" showdivider="$index > 0" titleimportant="false" postadded="newPostAdded()" defaultsubject="defaultSubject"></mma-mod-forum-discussion-post>
                 </article>
             </div>
         </mm-loading>