diff --git a/CHANGELOG.md b/CHANGELOG.md
index ae46ad302..e8a66f49b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,9 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Deprecated
 ### Removed
 ### Fixed
+- Added missing types for AwsSigv4SignerOptions.service ([#377](https://github.com/opensearch-project/opensearch-js/pull/377))
+
+
 ### Security
 - [CVE-2022-25912] Bumps simple-git from 3.4.0 to 3.15.0 ([#341](https://github.com/opensearch-project/opensearch-js/pull/341))
 
diff --git a/lib/aws/index.d.ts b/lib/aws/index.d.ts
index a36b701c8..3d8e5c652 100644
--- a/lib/aws/index.d.ts
+++ b/lib/aws/index.d.ts
@@ -19,6 +19,7 @@ import { OpenSearchClientError } from '../errors';
 interface AwsSigv4SignerOptions {
   getCredentials?: () => Promise<Credentials>;
   region: string;
+  service?: 'es' | 'aoss';
 }
 
 interface AwsSigv4SignerResponse {