diff --git a/index.d.ts b/index.d.ts
index 52ccff7..293d4bb 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -4,6 +4,6 @@ export interface IOptions {
   header: any;
 }
 
-export function decode(token: string, key: string, noVerify?: boolean, algorithm?: TAlgorithm): any;
+export function decode(token: string, key: string | Buffer, noVerify?: boolean, algorithm?: TAlgorithm): any;
 
-export function encode(payload: any, key: string, algorithm?: TAlgorithm, options?: IOptions): string;
+export function encode(payload: any, key: string | Buffer, algorithm?: TAlgorithm, options?: IOptions): string;