diff --git a/lib/nulla_web/controllers/user_controller.ex b/lib/nulla_web/controllers/user_controller.ex
index a5467e7..d85d580 100644
--- a/lib/nulla_web/controllers/user_controller.ex
+++ b/lib/nulla_web/controllers/user_controller.ex
@@ -16,7 +16,7 @@ defmodule NullaWeb.UserController do
     if accept in ["application/activity+json", "application/ld+json"] do
       conn
       |> put_resp_content_type("application/activity+json")
-      |> send_resp(200, ActivityPub.user(domain, user))
+      |> send_resp(200, Jason.encode!(ActivityPub.user(domain, user)))
     else
       following = Utils.count_following_by_username!(user.username)
       followers = Utils.count_followers_by_username!(user.username)