diff --git a/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php b/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
index f862970a7fd8..5792aa40828c 100644
--- a/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
+++ b/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
@@ -45,7 +45,7 @@ public function validate($form, Constraint $constraint)
 
             // Validate the data against the constraints defined
             // in the form
-            $constraints = $config->getOption('constraints');
+            $constraints = $config->getOption('constraints', array());
             foreach ($constraints as $constraint) {
                 foreach ($groups as $group) {
                     if (in_array($group, $constraint->groups)) {
diff --git a/src/Symfony/Component/Form/Tests/Extension/Validator/Constraints/FormValidatorTest.php b/src/Symfony/Component/Form/Tests/Extension/Validator/Constraints/FormValidatorTest.php
index c440a0470abb..1e30f237a563 100644
--- a/src/Symfony/Component/Form/Tests/Extension/Validator/Constraints/FormValidatorTest.php
+++ b/src/Symfony/Component/Form/Tests/Extension/Validator/Constraints/FormValidatorTest.php
@@ -123,6 +123,17 @@ public function testDontValidateIfParentWithoutCascadeValidation()
         $this->assertNoViolation();
     }
 
+    public function testNotExistingConstraintIndex()
+    {
+        $object = new \stdClass();
+        $form = new FormBuilder('name', '\stdClass', $this->dispatcher, $this->factory);
+        $form = $form->setData($object)->getForm();
+
+        $this->validator->validate($form, new Form());
+
+        $this->assertNoViolation();
+    }
+
     public function testValidateConstraintsEvenIfNoCascadeValidation()
     {
         $object = $this->getMock('\stdClass');