diff --git a/auth/shibboleth/index.php b/auth/shibboleth/index.php
index ff8a385090f..f798d402931 100644
--- a/auth/shibboleth/index.php
+++ b/auth/shibboleth/index.php
@@ -6,7 +6,7 @@
 
     $PAGE->set_url('/auth/shibboleth/index.php');
 
-    if (isloggedin() && $USER->username != 'guest') {      // Nothing to do
+    if (isloggedin() && !isguestuser()) {      // Nothing to do
         if (isset($SESSION->wantsurl) and (strpos($SESSION->wantsurl, $CFG->wwwroot) === 0)) {
             $urltogo = $SESSION->wantsurl;    /// Because it's an address in this site
             unset($SESSION->wantsurl);
diff --git a/blocks/online_users/block_online_users.php b/blocks/online_users/block_online_users.php
index decdb0ede04..70ddd2b6d0d 100644
--- a/blocks/online_users/block_online_users.php
+++ b/blocks/online_users/block_online_users.php
@@ -144,7 +144,7 @@ class block_online_users extends block_base {
                 $this->content->text .= '<li class="listentry">';
                 $timeago = format_time(time() - $user->lastaccess); //bruno to calculate correctly on frontpage
 
-                if ($user->username == 'guest') {
+                if (isguestuser($user)) {
                     $this->content->text .= '<div class="user">'.$OUTPUT->user_picture($user, array('size'=>16));
                     $this->content->text .= get_string('guestuser').'</div>';
 
@@ -152,7 +152,7 @@ class block_online_users extends block_base {
                     $this->content->text .= '<div class="user">'.$OUTPUT->user_picture($user, array('size'=>16));
                     $this->content->text .= '<a href="'.$CFG->wwwroot.'/user/view.php?id='.$user->id.'&amp;course='.$this->page->course->id.'" title="'.$timeago.'">'.$user->fullname.'</a></div>';
                 }
-                if ($canshowicon and ($USER->id != $user->id) and  $user->username != 'guest') {  // Only when logged in and messaging active etc
+                if ($canshowicon and ($USER->id != $user->id) and !isguestuser($user)) {  // Only when logged in and messaging active etc
                     $anchortagcontents = '<img class="iconsmall" src="'.$OUTPUT->pix_url('t/message') . '" alt="'. get_string('messageselectadd') .'" />';
                     $anchortag = '<a href="'.$CFG->wwwroot.'/message/index.php?id='.$user->id.'" title="'.get_string('messageselectadd').'">'.$anchortagcontents .'</a>';
 
diff --git a/course/recent_form.php b/course/recent_form.php
index b8f121c00db..a9f78ef41c3 100644
--- a/course/recent_form.php
+++ b/course/recent_form.php
@@ -51,9 +51,7 @@ class recent_form extends moodleform {
         if ($viewparticipants) {
             $options = array();
             $options[0] = get_string('allparticipants');
-            if ($guest = get_complete_user_data('username', 'guest')) {
-                $options[$guest->id] = fullname($guest);
-            }
+            $options[$CFG->siteguest] = get_string('guestuser');
 
             if (groups_get_course_groupmode($COURSE) == SEPARATEGROUPS) {
                 $groups = groups_get_user_groups($COURSE->id);
diff --git a/course/report/log/lib.php b/course/report/log/lib.php
index 3a7b6bc7a0f..420fcf530cc 100644
--- a/course/report/log/lib.php
+++ b/course/report/log/lib.php
@@ -104,9 +104,7 @@ function print_mnet_log_selector_form($hostid, $course, $selecteduser=0, $select
                 $users[$courseuser->id] = fullname($courseuser, has_capability('moodle/site:viewfullnames', $context));
             }
         }
-        if ($guest = get_complete_user_data('username', 'guest')) {
-            $users[$guest->id] = fullname($guest);
-        }
+        $users[$CFG->siteguest] = get_string('guestuser');
     }
 
     // Get all the hosts that have log records
@@ -368,9 +366,7 @@ function print_log_selector_form($course, $selecteduser=0, $selecteddate='today'
                 $users[$courseuser->id] = fullname($courseuser, has_capability('moodle/site:viewfullnames', $context));
             }
         }
-        if ($guest = get_complete_user_data('username', 'guest')) {
-            $users[$guest->id] = fullname($guest);
-        }
+        $users[$CFG->siteguest] = get_string('guestuser');
     }
 
     if (has_capability('coursereport/log:view', $sitecontext) && $showcourses) {