diff --git a/specs.json b/specs.json
index 87d2774f..5578ca6d 100644
--- a/specs.json
+++ b/specs.json
@@ -1047,6 +1047,7 @@
     }
   },
   "https://www.rfc-editor.org/rfc/rfc9218",
+  "https://www.rfc-editor.org/rfc/rfc9421",
   {
     "url": "https://www.rfc-editor.org/rfc/rfc9530",
     "formerNames": [