diff --git a/src/PhpImap/Mailbox.php b/src/PhpImap/Mailbox.php
index a4e5dbaa..9620dc7d 100644
--- a/src/PhpImap/Mailbox.php
+++ b/src/PhpImap/Mailbox.php
@@ -1093,7 +1093,7 @@ public function downloadAttachment($dataInfo, $params, $partStructure, $mailId,
             $fileName = $fileName;
         }
 
-        $attachmentId = sha1($fileName . ($partStructure->ifid ? $partStructure->id : ""));
+        $attachmentId = sha1($fileName.($partStructure->ifid ? $partStructure->id : ''));
 
         $attachment = new IncomingMailAttachment();
         $attachment->id = $attachmentId;