diff --git a/lib/Doctrine/Entities/ValidationSession.php b/lib/Doctrine/Entities/ValidationSession.php
index adb779ddfa..be6128b302 100644
--- a/lib/Doctrine/Entities/ValidationSession.php
+++ b/lib/Doctrine/Entities/ValidationSession.php
@@ -340,7 +340,7 @@ class ValidationSession
       return null;
     }
 
-    $date_obj = new DateTime();
+    $date_obj = new \DateTime();
 
     return $date_obj > $this->getExpires();
   }