diff --git a/src/super_archives/views.py b/src/super_archives/views.py
index 8cc0cf7..37c1537 100644
--- a/src/super_archives/views.py
+++ b/src/super_archives/views.py
@@ -74,6 +74,7 @@ class ThreadView(View):
             raise http.Http404
 
         data = {
+            'in_reply_to': thread.message_set.last().message_id,
             'email_from': request.user.email,
             'name_from': request.user.get_full_name(),
             'subject': thread.message_set.first().subject_clean,
--
libgit2 0.21.2