diff --git a/src/crypto.ts b/src/crypto.ts
index ad0c483..c450213 100644
--- a/src/crypto.ts
+++ b/src/crypto.ts
@@ -2,7 +2,7 @@ import crypto from "crypto";
 import * as core from "webcrypto-core";
 import { SubtleCrypto } from "./subtle";
 
-export class Crypto implements core.Crypto {
+export class Crypto extends core.Crypto {
 
   public subtle = new SubtleCrypto();