diff --git a/javascript/index.d.ts b/javascript/index.d.ts
index 3a1128d..141f695 100644
--- a/javascript/index.d.ts
+++ b/javascript/index.d.ts
@@ -125,3 +125,5 @@ declare class SAS {
 export function init(opts?: object): Promise<void>;
 
 export function get_library_version(): [number, number, number];
+
+export const PRIVATE_KEY_LENGTH: number;