diff --git a/lib/aws/index.d.ts b/lib/aws/index.d.ts
index 50ba0c4f0..640a46713 100644
--- a/lib/aws/index.d.ts
+++ b/lib/aws/index.d.ts
@@ -20,6 +20,7 @@ import { OpenSearchClientError } from '../errors';
 interface AwsSigv4SignerOptions {
   getCredentials: () => Promise<Credentials>;
   region: string;
+  service?: 'es' | 'aoss';
 }
 
 interface AwsSigv4SignerResponse {