diff --git a/src/v1/text_to_speech_client.ts b/src/v1/text_to_speech_client.ts
index 00cfe28b..f4d7eff5 100644
--- a/src/v1/text_to_speech_client.ts
+++ b/src/v1/text_to_speech_client.ts
@@ -121,6 +121,12 @@ export class TextToSpeechClient {
     // Save the auth object to the client, for use by other methods.
     this.auth = this._gaxGrpc.auth as gax.GoogleAuth;
 
+    // Set useJWTAccessWithScope on the auth object.
+    this.auth.useJWTAccessWithScope = true;
+
+    // Set defaultServicePath on the auth object.
+    this.auth.defaultServicePath = staticMembers.servicePath;
+
     // Set the default scopes in auth client if needed.
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;
diff --git a/src/v1beta1/text_to_speech_client.ts b/src/v1beta1/text_to_speech_client.ts
index c63349f1..e20a5273 100644
--- a/src/v1beta1/text_to_speech_client.ts
+++ b/src/v1beta1/text_to_speech_client.ts
@@ -121,6 +121,12 @@ export class TextToSpeechClient {
     // Save the auth object to the client, for use by other methods.
     this.auth = this._gaxGrpc.auth as gax.GoogleAuth;
 
+    // Set useJWTAccessWithScope on the auth object.
+    this.auth.useJWTAccessWithScope = true;
+
+    // Set defaultServicePath on the auth object.
+    this.auth.defaultServicePath = staticMembers.servicePath;
+
     // Set the default scopes in auth client if needed.
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;