diff --git a/phpBB/memberlist.php b/phpBB/memberlist.php
index cf0b724615..afa4ed8b4b 100644
--- a/phpBB/memberlist.php
+++ b/phpBB/memberlist.php
@@ -37,7 +37,7 @@ $start = ( isset($HTTP_GET_VARS['start']) ) ? intval($HTTP_GET_VARS['start']) :
 
 if ( isset($HTTP_GET_VARS['mode']) || isset($HTTP_POST_VARS['mode']) )
 {
-	$mode = ( isset($HTTP_POST_VARS['mode']) ) ? $HTTP_POST_VARS['mode'] : $HTTP_GET_VARS['mode'];
+	$mode = ( isset($HTTP_POST_VARS['mode']) ) ? htmlspecialchars($HTTP_POST_VARS['mode']) : htmlspecialchars($HTTP_GET_VARS['mode']);
 }
 else
 {