diff --git a/src/PostmarkHandler.php b/src/PostmarkHandler.php
index bb097c3..cdf7961 100644
--- a/src/PostmarkHandler.php
+++ b/src/PostmarkHandler.php
@@ -85,6 +85,7 @@ class PostmarkHandler {
       $reply_to = !empty($params['reply-to']) ? $params['reply-to'] : NULL;
       $cc = !empty($params['cc']) ? $params['cc'] : NULL;
       $bcc = !empty($params['bcc']) ? $params['bcc'] : NULL;
+      $attachment = !empty($params['attachment']) ? $params['attachment'] : NULL;
 
       $response = $this->postmarkClient->sendEmail(
         $sender_signature,
@@ -96,7 +97,9 @@ class PostmarkHandler {
         $track_opens,
         $reply_to,
         $cc,
-        $bcc
+        $bcc,
+        NULL,
+        $attachment
       );
 
       // Debug mode: log all messages.