diff --git a/normalization.php b/normalization.php
index 4cb9569181..069dabbc0f 100644
--- a/normalization.php
+++ b/normalization.php
@@ -72,7 +72,7 @@ $scripts = $header->getScripts();
 $scripts->addFile('normalization.js');
 $scripts->addFile('jquery/jquery.uitablefilter.js');
 $normalForm = '1nf';
-if (isset($_REQUEST['normalizeTo'])) {
+if (PMA_isValid($_REQUEST['normalizeTo'], array('1nf', '2nf', '3nf'))) {
     $normalForm = $_REQUEST['normalizeTo'];
 }
 if (isset($_REQUEST['createNewTables2NF'])) {