diff --git a/phpBB/viewtopic.php b/phpBB/viewtopic.php
index 2bc8086efe..e0584f3dc3 100644
--- a/phpBB/viewtopic.php
+++ b/phpBB/viewtopic.php
@@ -394,7 +394,8 @@ if (!isset($topic_tracking_info))
 $limit_days = array(0 => $user->lang['ALL_POSTS'], 1 => $user->lang['1_DAY'], 7 => $user->lang['7_DAYS'], 14 => $user->lang['2_WEEKS'], 30 => $user->lang['1_MONTH'], 90 => $user->lang['3_MONTHS'], 180 => $user->lang['6_MONTHS'], 365 => $user->lang['1_YEAR']);
 
 $sort_by_text = array('a' => $user->lang['AUTHOR'], 't' => $user->lang['POST_TIME'], 's' => $user->lang['SUBJECT']);
-$sort_by_sql = array('a' => 'u.username_clean', 't' => 'p.post_time', 's' => 'p.post_subject');
+$sort_by_sql = array('a' => array('u.username_clean', 'p.post_id'), 't' => 'p.post_time', 's' => array('p.post_subject', 'p.post_id'));
+$join_user_sql = array('a' => true, 't' => false, 's' => false);
 
 $s_limit_days = $s_sort_key = $s_sort_dir = $u_sort_param = '';
 
@@ -858,6 +859,7 @@ if (!empty($topic_data['poll_start']))
 // If the user is trying to reach the second half of the topic, fetch it starting from the end
 $store_reverse = false;
 $sql_limit = $config['posts_per_page'];
+$sql_sort_order = $direction = '';
 
 if ($start > $total_posts / 2)
 {
@@ -869,15 +871,24 @@ if ($start > $total_posts / 2)
 	}
 
 	// Select the sort order
-	$sql_sort_order = $sort_by_sql[$sort_key] . ' ' . (($sort_dir == 'd') ? 'ASC' : 'DESC');
+	$direction = (($sort_dir == 'd') ? 'ASC' : 'DESC');
 	$sql_start = max(0, $total_posts - $sql_limit - $start);
 }
 else
 {
 	// Select the sort order
-	$sql_sort_order = $sort_by_sql[$sort_key] . ' ' . (($sort_dir == 'd') ? 'DESC' : 'ASC');
+	$direction = (($sort_dir == 'd') ? 'DESC' : 'ASC');
 	$sql_start = $start;
 }
+if (is_array($sort_by_sql[$sort_key]))
+{
+	$sql_sort_order = implode(' ' . $direction . ', ', $sort_by_sql[$sort_key]) . ' ' . $direction;
+}
+else
+{
+	$sql_sort_order = $sort_by_sql[$sort_key] . ' ' . $direction;
+}
+
 
 // Container for user details, only process once
 $post_list = $user_cache = $id_cache = $attachments = $attach_list = $rowset = $update_count = $post_edit_list = array();
@@ -887,10 +898,10 @@ $i = $i_total = 0;
 
 // Go ahead and pull all data for this topic
 $sql = 'SELECT p.post_id
-	FROM ' . POSTS_TABLE . ' p' . (($sort_by_sql[$sort_key][0] == 'u') ? ', ' . USERS_TABLE . ' u': '') . "
+	FROM ' . POSTS_TABLE . ' p' . (($join_user_sql[$sort_key]) ? ', ' . USERS_TABLE . ' u': '') . "
 	WHERE p.topic_id = $topic_id
 		" . ((!$auth->acl_get('m_approve', $forum_id)) ? 'AND p.post_approved = 1' : '') . "
-		" . (($sort_by_sql[$sort_key][0] == 'u') ? 'AND u.user_id = p.poster_id': '') . "
+		" . (($join_user_sql[$sort_key]) ? 'AND u.user_id = p.poster_id': '') . "
 		$limit_posts_time
 	ORDER BY $sql_sort_order";
 $result = $db->sql_query_limit($sql, $sql_limit, $sql_start);