diff --git a/app/Helpers/NotificationHelper.php b/app/Helpers/NotificationHelper.php
index 39f8141ec..e6f817ed8 100644
--- a/app/Helpers/NotificationHelper.php
+++ b/app/Helpers/NotificationHelper.php
@@ -83,6 +83,9 @@ class NotificationHelper
             [
                 'path' => 'invoices/' . $invoice->number . '.pdf',
                 'name' => 'invoice.pdf',
+                'options' => [
+                    'mime' => 'application/pdf',
+                ],
             ],
         ];