diff --git a/mod/glossary/showentry.php b/mod/glossary/showentry.php
index 1a5936ab7b7..b1987211b77 100644
--- a/mod/glossary/showentry.php
+++ b/mod/glossary/showentry.php
@@ -2,7 +2,7 @@
     require_once("../../config.php");
     require_once("lib.php");
 
-    $concept  = optional_param('concept', '', PARAM_CLEAR);
+    $concept  = optional_param('concept', '', PARAM_CLEAN);
     $courseid = optional_param('courseid', 0, PARAM_INT);
     $eid      = optional_param('eid', 0, PARAM_INT); // glossary entry id
     $displayformat = optional_param('displayformat',-1, PARAM_INT);