diff --git a/samples/test/externalclient.test.js b/samples/test/externalclient.test.js
index b3e231c3..6f128529 100644
--- a/samples/test/externalclient.test.js
+++ b/samples/test/externalclient.test.js
@@ -290,7 +290,7 @@ describe('samples for external-account', () => {
       },
     });
     // Confirm expected script output.
-    assert.match(output, /DNS Info:/);
+    assert.match(output, /DNS Info:/, output);
   });
 
   it('should sign the blobs with IAM credentials API', async () => {
@@ -389,7 +389,7 @@ describe('samples for external-account', () => {
       },
     });
     // Confirm expected script output.
-    assert.match(output, /DNS Info:/);
+    assert.match(output, /DNS Info:/, output);
   });
 
   it('should acquire ADC for AWS creds', async () => {
@@ -427,7 +427,7 @@ describe('samples for external-account', () => {
       },
     });
     // Confirm expected script output.
-    assert.match(output, /DNS Info:/);
+    assert.match(output, /DNS Info:/, output);
   });
 
   it('should acquire ADC for PluggableAuth creds', async () => {
@@ -474,7 +474,7 @@ describe('samples for external-account', () => {
       },
     });
     // Confirm expected script output.
-    assert.match(output, /DNS Info:/);
+    assert.match(output, /DNS Info:/, output);
   });
 
   it('should acquire access token with service account impersonation options', async () => {
diff --git a/src/auth/oauth2client.ts b/src/auth/oauth2client.ts
index e5a94c31..c9f87d56 100644
--- a/src/auth/oauth2client.ts
+++ b/src/auth/oauth2client.ts
@@ -854,7 +854,7 @@ export class OAuth2Client extends AuthClient {
 
   protected async getRequestMetadataAsync(
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    url?: string | null
+    url?: string | URL | null
   ): Promise<RequestMetadataResponse> {
     const thisCreds = this.credentials;
     if (