diff --git a/Mail/EmailMessage.php b/Mail/EmailMessage.php
index a0d936f..0336af9 100644
--- a/Mail/EmailMessage.php
+++ b/Mail/EmailMessage.php
@@ -86,7 +86,7 @@ public function __construct(
         array $replyTo = null,
         $sender = null,
         $subject = '',
-        $encoding = ''
+        ?string $encoding = 'utf-8'
     ) {
         $this->message = new ZendMessage();
         $mimeMessage = new ZendMimeMessage();