diff --git a/lib/xmlize.php b/lib/xmlize.php
index 78cf82b2a87..a8ec8c8d9bc 100644
--- a/lib/xmlize.php
+++ b/lib/xmlize.php
@@ -39,6 +39,9 @@
 
 defined('MOODLE_INTERNAL') || die();
 
+// Add setuplib in case it has not been loaded yet as it's required by \xml_format_exception.
+require_once($CFG->libdir.'/setuplib.php');
+
 class xml_format_exception extends moodle_exception {
     /** @var string */
     public $errorstring;