diff --git a/src/Symfony/Component/Validator/Constraint.php b/src/Symfony/Component/Validator/Constraint.php
index fa6b4b4d26..372308ed48 100644
--- a/src/Symfony/Component/Validator/Constraint.php
+++ b/src/Symfony/Component/Validator/Constraint.php
@@ -274,7 +274,7 @@ abstract class Constraint
     public function __sleep()
     {
         // Initialize "groups" option if it is not set
-        $this->__get('groups');
+        $this->groups;
 
         return array_keys(get_object_vars($this));
     }
diff --git a/src/Symfony/Component/Validator/Tests/ConstraintTest.php b/src/Symfony/Component/Validator/Tests/ConstraintTest.php
index 6ccf661fa8..45b9b75c0f 100644
--- a/src/Symfony/Component/Validator/Tests/ConstraintTest.php
+++ b/src/Symfony/Component/Validator/Tests/ConstraintTest.php
@@ -167,22 +167,34 @@ class ConstraintTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($constraint, $restoredConstraint);
     }
 
-    public function testSerializeInitializesGroupsOption()
+    public function testSerializeInitializesGroupsOptionToDefault()
     {
-        $constraintWithExplicitGroup = new ConstraintA(array(
+        $constraint = new ConstraintA(array(
+            'property1' => 'foo',
+            'property2' => 'bar',
+        ));
+
+        $constraint = unserialize(serialize($constraint));
+
+        $expected = new ConstraintA(array(
             'property1' => 'foo',
             'property2' => 'bar',
             'groups' => 'Default',
         ));
 
-        $constraintWithoutExplicitGroup = new ConstraintA(array(
+        $this->assertEquals($expected, $constraint);
+    }
+
+    public function testSerializeKeepsCustomGroups()
+    {
+        $constraint = new ConstraintA(array(
             'property1' => 'foo',
             'property2' => 'bar',
+            'groups' => 'MyGroup',
         ));
 
-        $constraintWithExplicitGroup = unserialize(serialize($constraintWithExplicitGroup));
-        $constraintWithoutExplicitGroup = unserialize(serialize($constraintWithoutExplicitGroup));
+        $constraint = unserialize(serialize($constraint));
 
-        $this->assertEquals($constraintWithExplicitGroup, $constraintWithoutExplicitGroup);
+        $this->assertSame(array('MyGroup'), $constraint->groups);
     }
 }