diff --git a/src/Symfony/Component/Form/FormTypeGuesserChain.php b/src/Symfony/Component/Form/FormTypeGuesserChain.php
index 7c4f65b43579..988c5ebc3bbb 100644
--- a/src/Symfony/Component/Form/FormTypeGuesserChain.php
+++ b/src/Symfony/Component/Form/FormTypeGuesserChain.php
@@ -25,8 +25,12 @@ class FormTypeGuesserChain implements FormTypeGuesserInterface
      *
      * @throws UnexpectedTypeException if any guesser does not implement FormTypeGuesserInterface
      */
-    public function __construct(array $guessers)
+    public function __construct($guessers)
     {
+        if (!is_array($guessers) && !$guessers instanceof \Traversable) {
+            throw new UnexpectedTypeException($guessers, 'array or Traversable');
+        }
+
         foreach ($guessers as $guesser) {
             if (!$guesser instanceof FormTypeGuesserInterface) {
                 throw new UnexpectedTypeException($guesser, 'Symfony\Component\Form\FormTypeGuesserInterface');