diff --git a/types/index.d.ts b/types/index.d.ts
index 3957f6aa1..4252a9efa 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -654,6 +654,7 @@ export namespace Horizon {
     high_threshold: number;
   }
   interface Flags {
+    auth_immutable: boolean;
     auth_required: boolean;
     auth_revocable: boolean;
   }