diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 758754202..8789b5f81 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -2353,6 +2353,10 @@ class UnitOfWork implements PropertyChangedListener
                     return;
                 }
 
+                if ($entity instanceof Proxy && !$entity->__isInitialized__) {
+                    $entity->__load();
+                }
+
                 $entityVersion = $class->reflFields[$class->versionField]->getValue($entity);
 
                 if ($entityVersion != $lockVersion) {
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/OptimisticTest.php b/tests/Doctrine/Tests/ORM/Functional/Locking/OptimisticTest.php
index e6773dd6b..3ce6437f3 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Locking/OptimisticTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/OptimisticTest.php
@@ -150,6 +150,19 @@ class OptimisticTest extends \Doctrine\Tests\OrmFunctionalTestCase
         }
     }
 
+    public function testLockWorksWithProxy()
+    {
+        $test = new OptimisticStandard();
+        $test->name = 'test';
+        $this->_em->persist($test);
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $proxy = $this->_em->getReference('Doctrine\Tests\ORM\Functional\Locking\OptimisticStandard', $test->id);
+
+        $this->_em->lock($proxy, LockMode::OPTIMISTIC, 1);
+    }
+
     public function testOptimisticTimestampSetsDefaultValue()
     {
         $test = new OptimisticTimestamp();