diff --git a/lib/classes/session/manager.php b/lib/classes/session/manager.php
index 4ce12f52ac8..04c6c65f171 100644
--- a/lib/classes/session/manager.php
+++ b/lib/classes/session/manager.php
@@ -1013,7 +1013,7 @@ class manager {
         // This may take a long time...
         \core_php_time_limit::raise();
 
-        $maxlifetime = $CFG->sessiontimeout;
+        $maxlifetime = (int) $CFG->sessiontimeout;
 
         try {
             // Kill all sessions of deleted and suspended users without any hesitation.
@@ -1060,7 +1060,7 @@ class manager {
             $rs->close();
 
             // Delete expired sessions for guest user account, give them larger timeout, there is no security risk here.
-            $params = array('purgebefore' => (time() - ($maxlifetime * 5)), 'guestid'=>$CFG->siteguest);
+            $params = array('purgebefore' => (time() - $maxlifetime), 'guestid' => $CFG->siteguest);
             $rs = $DB->get_recordset_select('sessions', 'userid = :guestid AND timemodified < :purgebefore', $params, 'id DESC', 'id, sid');
             foreach ($rs as $session) {
                 self::kill_session($session->sid);