diff --git a/admin/permalinks.php b/admin/permalinks.php
index 5520a91c2..eaebb6c64 100644
--- a/admin/permalinks.php
+++ b/admin/permalinks.php
@@ -26,6 +26,12 @@ function parse_sort_variables(
     {
       $base_url .= $is_first ? '?' : '&';
       $is_first = false;
+
+      if (!in_array($key, array('page', 'psf', 'dpsf', 'pwg_token')))
+      {
+        fatal_error('unexpected URL get key');
+      }
+
       $base_url .= urlencode($key).'='.urlencode($value);
     }
   }