diff --git a/lib/aws.ts b/lib/aws.ts
index 4e5a523..a761c21 100644
--- a/lib/aws.ts
+++ b/lib/aws.ts
@@ -163,7 +163,7 @@ export class DefaultAwsClient implements IAws {
         RoleArn: roleArn,
         ExternalId: externalId,
         RoleSessionName: `cdk-assets-${safeUsername()}`,
-        // ...(additionalOptions ?? {}),
+        ...(additionalOptions ?? {}),
       },
       stsConfig: {
         region,
diff --git a/test/aws.test.ts b/test/aws.test.ts
index 8d6e498..3282cbe 100644
--- a/test/aws.test.ts
+++ b/test/aws.test.ts
@@ -1,10 +1,6 @@
 import * as os from 'os';
 import { DefaultAwsClient } from '../lib';
 
-afterEach(() => {
-  jest.requireActual('aws-sdk');
-});
-
 beforeEach(() => {
   jest.requireActual('aws-sdk');
 });
@@ -60,7 +56,7 @@ test('assumeRole passes the right parameters to STS', async () => {
 
 test('assumeRole defaults session tags to all', async () => {
   // eslint-disable-next-line @typescript-eslint/no-require-imports
-  require('aws-sdk');
+  const AWS = require('aws-sdk');
 
   jest.mock('aws-sdk', () => {
     return {
@@ -75,13 +71,36 @@ test('assumeRole defaults session tags to all', async () => {
       ChainableTemporaryCredentials: jest.fn(),
     };
   });
-
   const aws = new DefaultAwsClient();
-
-  const account = await aws.discoverTargetAccount({});
-  expect(account).toEqual({
-    accountId: '123456789012',
-    partition: 'aws',
+  await withMocked(os, 'userInfo', async (userInfo) => {
+    userInfo.mockReturnValue({
+      username: 'foo',
+      uid: 1,
+      gid: 1,
+      homedir: '/here',
+      shell: '/bin/sh',
+    });
+    await aws.discoverTargetAccount({
+      region: 'us-east-1',
+      assumeRoleArn: 'arn:aws:iam::123456789012:role/my-role',
+      assumeRoleExternalId: 'external-id',
+      assumeRoleAdditionalOptions: {
+        Tags: [{ Key: 'Departement', Value: 'Engineering' }],
+      },
+    });
+    expect(AWS.ChainableTemporaryCredentials).toHaveBeenCalledWith({
+      params: {
+        ExternalId: 'external-id',
+        RoleArn: 'arn:aws:iam::123456789012:role/my-role',
+        Tags: [{ Key: 'Departement', Value: 'Engineering' }],
+        TransitiveTagKeys: ['Departement'],
+        RoleSessionName: `cdk-assets-foo`,
+      },
+      stsConfig: {
+        customUserAgent: 'cdk-assets',
+        region: 'us-east-1',
+      },
+    });
   });
 });