diff -r f8797e3284ff -r 2393dbae51ed mod_http_oauth2/mod_http_oauth2.lua
--- a/mod_http_oauth2/mod_http_oauth2.lua	Wed May 03 10:55:22 2023 +0200
+++ b/mod_http_oauth2/mod_http_oauth2.lua	Thu May 04 18:41:33 2023 +0200
@@ -77,7 +77,9 @@
 -- Used to derive client_secret from client_id, set to enable stateless dynamic registration.
 local registration_key = module:get_option_string("oauth2_registration_key");
 local registration_algo = module:get_option_string("oauth2_registration_algorithm", "HS256");
-local registration_options = module:get_option("oauth2_registration_options", { default_ttl = 60 * 60 * 24 * 90 });
+local registration_ttl = module:get_option("oauth2_registration_ttl", nil);
+local registration_options = module:get_option("oauth2_registration_options",
+	{ default_ttl = registration_ttl; accept_expired = not registration_ttl });
 
 local pkce_required = module:get_option_boolean("oauth2_require_code_challenge", false);