diff --git a/src/Fetch/Message.php b/src/Fetch/Message.php
index e382678..40b672a 100755
--- a/src/Fetch/Message.php
+++ b/src/Fetch/Message.php
@@ -469,7 +469,7 @@ public function getDate()
     /**
      * This returns the subject of the message.
      *
-     * @return string
+     * @return string|null
      */
     public function getSubject()
     {