diff --git a/src/Mailgun/Message/BatchMessage.php b/src/Mailgun/Message/BatchMessage.php
index d10b582..b861a0f 100644
--- a/src/Mailgun/Message/BatchMessage.php
+++ b/src/Mailgun/Message/BatchMessage.php
@@ -98,6 +98,7 @@ class BatchMessage extends MessageBuilder
     }
 
     /**
+     * @throws RuntimeException
      * @throws MissingRequiredParameter
      */
     public function finalize()