diff --git a/types/scrypt-js/index.d.ts b/types/scrypt-js/index.d.ts
index e3ee7fa68f..fde3c0a444 100644
--- a/types/scrypt-js/index.d.ts
+++ b/types/scrypt-js/index.d.ts
@@ -15,7 +15,7 @@ declare function scrypt(
     callback: (
         error: Error | undefined | null,
         progress: number,
-        key?: string,
+        key?: ReadonlyArray<number>,
     ) => void
 ): void;
 
diff --git a/types/scrypt-js/scrypt-js-tests.ts b/types/scrypt-js/scrypt-js-tests.ts
index 21c77fb16c..c0b3c41a9c 100644
--- a/types/scrypt-js/scrypt-js-tests.ts
+++ b/types/scrypt-js/scrypt-js-tests.ts
@@ -1,7 +1,7 @@
 import scrypt = require('scrypt-js');
 
 const testBuffer = Buffer.from('test');
-const testCB = (err: Error | undefined | null, progress: number) => {};
+const testCB = (err: Error | undefined | null, progress: number, key?: ReadonlyArray<number>) => {};
 
 // $ExpectType void
 scrypt(testBuffer, testBuffer, 1, 1, 1, 1, testCB);