diff --git a/types/index.d.ts b/types/index.d.ts
index 910cffb..4370c6d 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -93,7 +93,7 @@ declare class IdTokenVerifier {
    * @param {string} [requestedNonce] nonce value that should match the one in the id_token claims
    * @param {verifyCallback} cb callback used to notify the results of the validation
    */
-  verify(token: string, requestedNonce?: string, cb: verifyCallback): any;
+  verify(token: string, requestedNonce: string | undefined, cb: verifyCallback): any;
   getRsaVerifier(iss: any, kid: any, cb: any): void;
   /**
    * @typedef DecodedToken