diff --git a/Manager/RepositoryManager.php b/Manager/RepositoryManager.php
index 337f32a..a780880 100644
--- a/Manager/RepositoryManager.php
+++ b/Manager/RepositoryManager.php
@@ -14,8 +14,8 @@ use RuntimeException;
  */
 class RepositoryManager implements RepositoryManagerInterface
 {
-    protected $entities;
-    protected $repositories;
+    protected $entities = array();
+    protected $repositories = array();
 
     public function addEntity($entityName, FinderInterface $finder, $repositoryName = null)
     {