diff --git a/django_yubin/admin.py b/django_yubin/admin.py
index 11215b1..5a2fdcf 100644
--- a/django_yubin/admin.py
+++ b/django_yubin/admin.py
@@ -134,7 +134,7 @@ def download_view(self, request, pk, signature):
         msg = instance.get_message_parser()
         attachment = mailparser_utils.get_attachment(msg, signature)
         response = HttpResponse(content_type=attachment['mail_content_type'])
-        response['Content-Disposition'] = attachment['content-disposition']
+        response['Content-Disposition'] = str(attachment['content-disposition'])
         response.write(mailparser_utils.get_content(attachment))
         return response