diff --git a/src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerAdapter.php b/src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerAdapter.php
index d9609b1a7b..8f7e809d6c 100644
--- a/src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerAdapter.php
+++ b/src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerAdapter.php
@@ -3,6 +3,8 @@
 final class PhabricatorMailImplementationPHPMailerAdapter
   extends PhabricatorMailImplementationAdapter {
 
+  private $mailer;
+
   /**
    * @phutil-external-symbol class PHPMailer
    */