diff --git a/include/ws_functions/pwg.categories.php b/include/ws_functions/pwg.categories.php
index f98c2eb34..2763ad20b 100644
--- a/include/ws_functions/pwg.categories.php
+++ b/include/ws_functions/pwg.categories.php
@@ -576,7 +576,7 @@ function ws_categories_add($params, &$service)
 
   global $conf;
 
-  if ($params["position"] != "") 
+  if (!empty($params['position']) and in_array($params['position'], array('first','last')))
   {
     //TODO make persistent with user prefs
     $conf['newcat_default_position'] = $params["position"];
diff --git a/ws.php b/ws.php
index b3d9d507e..6cb3428cf 100644
--- a/ws.php
+++ b/ws.php
@@ -611,7 +611,7 @@ function ws_addDefaultMethods( $arr )
                                 'info'=>'public, private'),
         'commentable' =>  array('default'=>true,
                                 'type'=>WS_TYPE_BOOL),
-        'position' =>     array('default'=>null),
+        'position' =>     array('default'=>null, 'info'=>'first, last'),
         ),
       'Adds an album.',
       $ws_functions_root . 'pwg.categories.php',