diff --git a/lib/Mailer/Mailer.php b/lib/Mailer/Mailer.php
index aa743aeeec..17de250842 100644
--- a/lib/Mailer/Mailer.php
+++ b/lib/Mailer/Mailer.php
@@ -40,7 +40,7 @@ class Mailer {
     return $this->mailer_instance->send($newsletter, $subscriber, $extra_params);
   }
 
-  function buildMailer() {
+  private function buildMailer() {
     switch ($this->mailer_config['method']) {
       case self::METHOD_AMAZONSES:
         $mailer_instance = new $this->mailer_config['class'](