diff --git a/src/Symfony/Component/Form/Form.php b/src/Symfony/Component/Form/Form.php
index 0ad79f70c7..a159aea6cc 100644
--- a/src/Symfony/Component/Form/Form.php
+++ b/src/Symfony/Component/Form/Form.php
@@ -340,12 +340,8 @@ class Form implements \IteratorAggregate, FormInterface
         if (!empty($clientData)) {
             $dataClass = $this->config->getDataClass();
 
-            if (null === $dataClass && is_object($clientData)) {
-                $expectedType = 'scalar';
-
-                if (count($this->children) > 0 && $this->config->getDataMapper()) {
-                    $expectedType = 'array';
-                }
+            if (null === $dataClass && is_object($clientData) && !$clientData instanceof \ArrayAccess) {
+                $expectedType = 'scalar, array or an instance of \ArrayAccess';
 
                 throw new FormException(
                     'The form\'s client data is expected to be of type ' . $expectedType . ', ' .
diff --git a/src/Symfony/Component/Form/Tests/FormTest.php b/src/Symfony/Component/Form/Tests/FormTest.php
index a15c9d6a40..389d5b4747 100644
--- a/src/Symfony/Component/Form/Tests/FormTest.php
+++ b/src/Symfony/Component/Form/Tests/FormTest.php
@@ -1249,6 +1249,21 @@ class FormTest extends \PHPUnit_Framework_TestCase
         $form->setData('foo');
     }
 
+    public function testClientDataMayBeArrayAccessIfDataClassIsNull()
+    {
+        $arrayAccess = $this->getMock('\ArrayAccess');
+        $config = new FormConfig('name', null, $this->dispatcher);
+        $config->appendClientTransformer(new FixedDataTransformer(array(
+            '' => '',
+            'foo' => $arrayAccess,
+        )));
+        $form = new Form($config);
+
+        $form->setData('foo');
+
+        $this->assertSame($arrayAccess, $form->getClientData());
+    }
+
     /**
      * @expectedException Symfony\Component\Form\Exception\FormException
      */