diff --git a/src/Symfony/Component/Security/Acl/Domain/ObjectIdentity.php b/src/Symfony/Component/Security/Acl/Domain/ObjectIdentity.php
index 907b1d8df8..fc5b9c6de6 100644
--- a/src/Symfony/Component/Security/Acl/Domain/ObjectIdentity.php
+++ b/src/Symfony/Component/Security/Acl/Domain/ObjectIdentity.php
@@ -36,7 +36,7 @@ final class ObjectIdentity implements ObjectIdentityInterface
      */
     public function __construct($identifier, $type)
     {
-        if (empty($identifier)) {
+        if ('' === $identifier) {
             throw new \InvalidArgumentException('$identifier cannot be empty.');
         }
         if (empty($type)) {
@@ -66,7 +66,7 @@ final class ObjectIdentity implements ObjectIdentityInterface
             if ($domainObject instanceof DomainObjectInterface) {
                 return new self($domainObject->getObjectIdentifier(), ClassUtils::getRealClass($domainObject));
             } elseif (method_exists($domainObject, 'getId')) {
-                return new self($domainObject->getId(), ClassUtils::getRealClass($domainObject));
+                return new self((string) $domainObject->getId(), ClassUtils::getRealClass($domainObject));
             }
         } catch (\InvalidArgumentException $invalid) {
             throw new InvalidDomainObjectException($invalid->getMessage(), 0, $invalid);
diff --git a/src/Symfony/Component/Security/Tests/Acl/Domain/ObjectIdentityTest.php b/src/Symfony/Component/Security/Tests/Acl/Domain/ObjectIdentityTest.php
index 9281fd53e4..111ae8a984 100644
--- a/src/Symfony/Component/Security/Tests/Acl/Domain/ObjectIdentityTest.php
+++ b/src/Symfony/Component/Security/Tests/Acl/Domain/ObjectIdentityTest.php
@@ -64,6 +64,26 @@ namespace Symfony\Component\Security\Tests\Acl\Domain
             $this->assertEquals('Symfony\Component\Security\Tests\Acl\Domain\TestDomainObject', $id->getType());
         }
 
+        public function testFromDomainObjectWithoutInterfaceEnforcesStringIdentifier()
+        {
+            $domainObject = new TestDomainObject();
+            $domainObject->id = 1;
+            $id = ObjectIdentity::fromDomainObject($domainObject);
+
+            $this->assertSame('1', $id->getIdentifier());
+            $this->assertEquals('Symfony\Component\Security\Tests\Acl\Domain\TestDomainObject', $id->getType());
+        }
+
+        public function testFromDomainObjectWithoutInterfaceAllowsZeroAsIdentifier()
+        {
+            $domainObject = new TestDomainObject();
+            $domainObject->id = '0';
+            $id = ObjectIdentity::fromDomainObject($domainObject);
+
+            $this->assertSame('0', $id->getIdentifier());
+            $this->assertEquals('Symfony\Component\Security\Tests\Acl\Domain\TestDomainObject', $id->getType());
+        }
+
         /**
          * @dataProvider getCompareData
          */
@@ -89,6 +109,8 @@ namespace Symfony\Component\Security\Tests\Acl\Domain
 
     class TestDomainObject
     {
+        public $id = 'getId()';
+
         public function getObjectIdentifier()
         {
             return 'getObjectIdentifier()';
@@ -96,7 +118,7 @@ namespace Symfony\Component\Security\Tests\Acl\Domain
 
         public function getId()
         {
-            return 'getId()';
+            return $this->id;
         }
     }
 }