symfony
diff --git a/‎src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueValidatorTest.php
Lines changed: 46 additions & 0 deletions b/‎src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueValidatorTest.php
Lines changed: 46 additions & 0 deletions
diff --git a/‎src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
Lines changed: 8 additions & 0 deletions b/‎src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
Lines changed: 8 additions & 0 deletions
@@ -367,4 +367,50 @@ public function testAssociatedCompositeEntity()
         );
         $violationsList = $validator->validate($associated);
     }
+
+    public function testDedicatedEntityManagerNullObject()
+    {
+        $uniqueFields = array('name');
+        $entityManagerName = 'foo'; 
+
+        $registry = $this->getMock('Doctrine\Common\Persistence\ManagerRegistry');
+
+        $constraint = new UniqueEntity(array(
+            'fields' => $uniqueFields,
+            'em' => $entityManagerName,
+        ));
+
+        $uniqueValidator = new UniqueEntityValidator($registry);
+
+        $entity = new SingleIntIdEntity(1, null);
+
+        $this->setExpectedException(
+            'Symfony\Component\Validator\Exception\ConstraintDefinitionException',
+            'Object manager "foo" does not exist.'
+        );
+
+        $uniqueValidator->validate($entity, $constraint);
+    }
+
+    public function testEntityManagerNullObject()
+    {
+        $uniqueFields = array('name');
+
+        $registry = $this->getMock('Doctrine\Common\Persistence\ManagerRegistry');
+
+        $constraint = new UniqueEntity(array(
+            'fields' => $uniqueFields,
+        ));
+
+        $uniqueValidator = new UniqueEntityValidator($registry);
+
+        $entity = new SingleIntIdEntity(1, null);
+
+        $this->setExpectedException(
+            'Symfony\Component\Validator\Exception\ConstraintDefinitionException',
+            'Unable to find the object manager associated with an entity of class "Symfony\Bridge\Doctrine\Tests\Fixtures\SingleIntIdEntity"'
+        );
+
+        $uniqueValidator->validate($entity, $constraint);
+    }
 }
@@ -62,8 +62,16 @@ public function validate($entity, Constraint $constraint)
 
         if ($constraint->em) {
             $em = $this->registry->getManager($constraint->em);
+
+            if (!$em) {
+               throw new ConstraintDefinitionException(sprintf('Object manager "%s" does not exist.', $constraint->em));
+            }
         } else {
             $em = $this->registry->getManagerForClass(get_class($entity));
+
+            if (!$em) {
+                throw new ConstraintDefinitionException(sprintf('Unable to find the object manager associated with an entity of class "%s".', get_class($entity)));
+            }
         }
 
         $className = $this->context->getClassName();