diff --git a/src/Fetch/Message.php b/src/Fetch/Message.php
index cab27f8..06ffc7c 100644
--- a/src/Fetch/Message.php
+++ b/src/Fetch/Message.php
@@ -201,7 +201,7 @@ class Message
 
             return false;
 
-        $this->subject = $messageOverview->subject;
+        $this->subject = isset($messageOverview->subject) ? $messageOverview->subject : null;
         $this->date    = strtotime($messageOverview->date);
         $this->size    = $messageOverview->size;