diff --git a/src/Symfony/Component/Validator/Constraints/Composite.php b/src/Symfony/Component/Validator/Constraints/Composite.php
index ab8466bcfc..d1391bb072 100644
--- a/src/Symfony/Component/Validator/Constraints/Composite.php
+++ b/src/Symfony/Component/Validator/Constraints/Composite.php
@@ -67,6 +67,10 @@ abstract class Composite extends Constraint
 
         foreach ($nestedConstraints as $constraint) {
             if (!$constraint instanceof Constraint) {
+                if (is_object($constraint)) {
+                    $constraint = get_class($constraint);
+                }
+
                 throw new ConstraintDefinitionException(sprintf('The value %s is not an instance of Constraint in constraint %s', $constraint, get_class($this)));
             }
 
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/CompositeTest.php b/src/Symfony/Component/Validator/Tests/Constraints/CompositeTest.php
index 6a8530723f..df4255007c 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/CompositeTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/CompositeTest.php
@@ -125,6 +125,17 @@ class CompositeTest extends TestCase
         ));
     }
 
+    /**
+     * @expectedException \Symfony\Component\Validator\Exception\ConstraintDefinitionException
+     */
+    public function testFailIfNoConstraintObject()
+    {
+        new ConcreteComposite(array(
+            new NotNull(array('groups' => 'Default')),
+            new \ArrayObject(),
+        ));
+    }
+
     /**
      * @expectedException \Symfony\Component\Validator\Exception\ConstraintDefinitionException
      */