diff --git a/lib/weblib.php b/lib/weblib.php
index 728c041318a..1dcd953130a 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1091,6 +1091,8 @@ function filter_text($text, $courseid=NULL) {
 
     global $CFG;
 
+    require_once($CFG->libdir.'/filterlib.php');
+
     if (!empty($CFG->textfilters)) {
         $textfilters = explode(',', $CFG->textfilters);
         foreach ($textfilters as $textfilter) {