--- a/mod_http_auth_check/mod_http_auth_check.lua	Tue Feb 20 14:59:03 2018 +0000
+++ b/mod_http_auth_check/mod_http_auth_check.lua	Tue Feb 20 17:30:17 2018 +0100
@@ -14,7 +14,8 @@
 	local response = event.response;
 	local headers = request.headers;
 	if not headers.authorization then
-		return 400
+		response.headers.www_authenticate = ("Basic realm=%q"):format(realm);
+		return 401
 	end
 	local from_jid, password = b64_decode(headers.authorization:match"[^ ]*$"):match"([^:]*):(.*)";
 	from_jid = jid_prep(from_jid);