diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 0eb7c8fd8..cb1f76958 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -1736,6 +1736,8 @@ class UnitOfWork implements PropertyChangedListener
                 $associatedId        = $this->getEntityIdentifier($idValue);
 
                 $flatId[$idField] = $associatedId[$targetClassMetadata->identifier[0]];
+            } else {
+                $flatId[$idField] = $idValue;
             }
         }