diff --git a/sha1/index.d.ts b/sha1/index.d.ts
index 3fbc990b23..58d931b26e 100644
--- a/sha1/index.d.ts
+++ b/sha1/index.d.ts
@@ -11,5 +11,10 @@
  * @param {(string | Buffer)} message - a string or buffer to hash
  * @returns {string} the resultant SHA1 hash of the given message
  */
-declare function main(message: string | Buffer): string;
+declare function main(message: string | Buffer, options?: Sha1Options): string | Uint8Array;
 export = main;
+
+interface Sha1Options {
+  asBytes?: boolean;
+  asString?: boolean;
+}