diff --git a/src/v1/publisher_client.ts b/src/v1/publisher_client.ts
index 6dcab350b..3b127acfb 100644
--- a/src/v1/publisher_client.ts
+++ b/src/v1/publisher_client.ts
@@ -17,8 +17,8 @@
 // ** All changes to this file may be overwritten. **
 
 /* global window */
-import * as gax from 'google-gax';
-import {
+import type * as gax from 'google-gax';
+import type {
   Callback,
   CallOptions,
   Descriptors,
@@ -28,7 +28,6 @@ import {
   IamClient,
   IamProtos,
 } from 'google-gax';
-
 import {Transform} from 'stream';
 import * as protos from '../../protos/protos';
 import jsonProtos = require('../../protos/protos.json');
@@ -38,7 +37,6 @@ import jsonProtos = require('../../protos/protos.json');
  * This file defines retry strategy and timeouts for all API methods in this library.
  */
 import * as gapicConfig from './publisher_client_config.json';
-
 const version = require('../../../package.json').version;
 
 /**
@@ -100,8 +98,18 @@ export class PublisherClient {
    *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
    *     For more information, please check the
    *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
+   * @param {gax} [gaxInstance]: loaded instance of `google-gax`. Useful if you
+   *     need to avoid loading the default gRPC version and want to use the fallback
+   *     HTTP implementation. Load only fallback version and pass it to the constructor:
+   *     ```
+   *     const gax = require('google-gax/build/src/fallback'); // avoids loading google-gax with gRPC
+   *     const client = new PublisherClient({fallback: 'rest'}, gax);
+   *     ```
    */
-  constructor(opts?: ClientOptions) {
+  constructor(
+    opts?: ClientOptions,
+    gaxInstance?: typeof gax | typeof gax.fallback
+  ) {
     // Ensure that options include all the required fields.
     const staticMembers = this.constructor as typeof PublisherClient;
     const servicePath =
@@ -121,8 +129,13 @@ export class PublisherClient {
       opts['scopes'] = staticMembers.scopes;
     }
 
+    // Load google-gax module synchronously if needed
+    if (!gaxInstance) {
+      gaxInstance = require('google-gax') as typeof gax;
+    }
+
     // Choose either gRPC or proto-over-HTTP implementation of google-gax.
-    this._gaxModule = opts.fallback ? gax.fallback : gax;
+    this._gaxModule = opts.fallback ? gaxInstance.fallback : gaxInstance;
 
     // Create a `gaxGrpc` object, with any grpc-specific options sent to the client.
     this._gaxGrpc = new this._gaxModule.GrpcClient(opts);
@@ -143,7 +156,7 @@ export class PublisherClient {
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;
     }
-    this.iamClient = new IamClient(this._gaxGrpc, opts);
+    this.iamClient = new this._gaxModule.IamClient(this._gaxGrpc, opts);
 
     // Determine the client header string.
     const clientHeader = [`gax/${this._gaxModule.version}`, `gapic/${version}`];
@@ -214,7 +227,7 @@ export class PublisherClient {
         'messages',
         ['topic'],
         'message_ids',
-        gax.createByteLengthFunction(
+        this._gaxModule.GrpcClient.createByteLengthFunction(
           // eslint-disable-next-line @typescript-eslint/no-explicit-any
           protoFilesRoot.lookupType('google.pubsub.v1.PubsubMessage') as any
         )
@@ -235,7 +248,7 @@ export class PublisherClient {
     this.innerApiCalls = {};
 
     // Add a warn function to the client constructor so it can be easily tested.
-    this.warn = gax.warn;
+    this.warn = this._gaxModule.warn;
   }
 
   /**
@@ -476,7 +489,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         name: request.name || '',
       });
     this.initialize();
@@ -564,7 +577,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         'topic.name': request.topic!.name || '',
       });
     this.initialize();
@@ -649,7 +662,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     this.initialize();
@@ -731,7 +744,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     this.initialize();
@@ -817,7 +830,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     this.initialize();
@@ -902,7 +915,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -996,7 +1009,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     this.initialize();
@@ -1037,7 +1050,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listTopics'];
@@ -1085,7 +1098,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listTopics'];
@@ -1192,7 +1205,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     this.initialize();
@@ -1237,7 +1250,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     const defaultCallSettings = this._defaults['listTopicSubscriptions'];
@@ -1285,7 +1298,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     const defaultCallSettings = this._defaults['listTopicSubscriptions'];
@@ -1390,7 +1403,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     this.initialize();
@@ -1431,7 +1444,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     const defaultCallSettings = this._defaults['listTopicSnapshots'];
@@ -1479,7 +1492,7 @@ export class PublisherClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         topic: request.topic || '',
       });
     const defaultCallSettings = this._defaults['listTopicSnapshots'];
diff --git a/src/v1/schema_service_client.ts b/src/v1/schema_service_client.ts
index c8170bd63..b832a5889 100644
--- a/src/v1/schema_service_client.ts
+++ b/src/v1/schema_service_client.ts
@@ -17,8 +17,8 @@
 // ** All changes to this file may be overwritten. **
 
 /* global window */
-import * as gax from 'google-gax';
-import {
+import type * as gax from 'google-gax';
+import type {
   Callback,
   CallOptions,
   Descriptors,
@@ -28,7 +28,6 @@ import {
   IamClient,
   IamProtos,
 } from 'google-gax';
-
 import {Transform} from 'stream';
 import * as protos from '../../protos/protos';
 import jsonProtos = require('../../protos/protos.json');
@@ -38,7 +37,6 @@ import jsonProtos = require('../../protos/protos.json');
  * This file defines retry strategy and timeouts for all API methods in this library.
  */
 import * as gapicConfig from './schema_service_client_config.json';
-
 const version = require('../../../package.json').version;
 
 /**
@@ -99,8 +97,18 @@ export class SchemaServiceClient {
    *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
    *     For more information, please check the
    *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
+   * @param {gax} [gaxInstance]: loaded instance of `google-gax`. Useful if you
+   *     need to avoid loading the default gRPC version and want to use the fallback
+   *     HTTP implementation. Load only fallback version and pass it to the constructor:
+   *     ```
+   *     const gax = require('google-gax/build/src/fallback'); // avoids loading google-gax with gRPC
+   *     const client = new SchemaServiceClient({fallback: 'rest'}, gax);
+   *     ```
    */
-  constructor(opts?: ClientOptions) {
+  constructor(
+    opts?: ClientOptions,
+    gaxInstance?: typeof gax | typeof gax.fallback
+  ) {
     // Ensure that options include all the required fields.
     const staticMembers = this.constructor as typeof SchemaServiceClient;
     const servicePath =
@@ -120,8 +128,13 @@ export class SchemaServiceClient {
       opts['scopes'] = staticMembers.scopes;
     }
 
+    // Load google-gax module synchronously if needed
+    if (!gaxInstance) {
+      gaxInstance = require('google-gax') as typeof gax;
+    }
+
     // Choose either gRPC or proto-over-HTTP implementation of google-gax.
-    this._gaxModule = opts.fallback ? gax.fallback : gax;
+    this._gaxModule = opts.fallback ? gaxInstance.fallback : gaxInstance;
 
     // Create a `gaxGrpc` object, with any grpc-specific options sent to the client.
     this._gaxGrpc = new this._gaxModule.GrpcClient(opts);
@@ -142,7 +155,7 @@ export class SchemaServiceClient {
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;
     }
-    this.iamClient = new IamClient(this._gaxGrpc, opts);
+    this.iamClient = new this._gaxModule.IamClient(this._gaxGrpc, opts);
 
     // Determine the client header string.
     const clientHeader = [`gax/${this._gaxModule.version}`, `gapic/${version}`];
@@ -208,7 +221,7 @@ export class SchemaServiceClient {
     this.innerApiCalls = {};
 
     // Add a warn function to the client constructor so it can be easily tested.
-    this.warn = gax.warn;
+    this.warn = this._gaxModule.warn;
   }
 
   /**
@@ -424,7 +437,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     this.initialize();
@@ -510,7 +523,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         name: request.name || '',
       });
     this.initialize();
@@ -592,7 +605,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         name: request.name || '',
       });
     this.initialize();
@@ -676,7 +689,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     this.initialize();
@@ -768,7 +781,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     this.initialize();
@@ -866,7 +879,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     this.initialize();
@@ -911,7 +924,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     const defaultCallSettings = this._defaults['listSchemas'];
@@ -963,7 +976,7 @@ export class SchemaServiceClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         parent: request.parent || '',
       });
     const defaultCallSettings = this._defaults['listSchemas'];
diff --git a/src/v1/subscriber_client.ts b/src/v1/subscriber_client.ts
index aa7b24780..14e3fd07d 100644
--- a/src/v1/subscriber_client.ts
+++ b/src/v1/subscriber_client.ts
@@ -17,21 +17,18 @@
 // ** All changes to this file may be overwritten. **
 
 /* global window */
-import * as gax from 'google-gax';
-import {
+import type * as gax from 'google-gax';
+import type {
   Callback,
   CallOptions,
   Descriptors,
   ClientOptions,
   PaginationCallback,
   GaxCall,
-  GoogleError,
   IamClient,
   IamProtos,
 } from 'google-gax';
-
-import {Transform} from 'stream';
-import {PassThrough} from 'stream';
+import {Transform, PassThrough} from 'stream';
 import * as protos from '../../protos/protos';
 import jsonProtos = require('../../protos/protos.json');
 /**
@@ -40,7 +37,6 @@ import jsonProtos = require('../../protos/protos.json');
  * This file defines retry strategy and timeouts for all API methods in this library.
  */
 import * as gapicConfig from './subscriber_client_config.json';
-
 const version = require('../../../package.json').version;
 
 /**
@@ -103,8 +99,18 @@ export class SubscriberClient {
    *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
    *     For more information, please check the
    *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
+   * @param {gax} [gaxInstance]: loaded instance of `google-gax`. Useful if you
+   *     need to avoid loading the default gRPC version and want to use the fallback
+   *     HTTP implementation. Load only fallback version and pass it to the constructor:
+   *     ```
+   *     const gax = require('google-gax/build/src/fallback'); // avoids loading google-gax with gRPC
+   *     const client = new SubscriberClient({fallback: 'rest'}, gax);
+   *     ```
    */
-  constructor(opts?: ClientOptions) {
+  constructor(
+    opts?: ClientOptions,
+    gaxInstance?: typeof gax | typeof gax.fallback
+  ) {
     // Ensure that options include all the required fields.
     const staticMembers = this.constructor as typeof SubscriberClient;
     const servicePath =
@@ -124,8 +130,13 @@ export class SubscriberClient {
       opts['scopes'] = staticMembers.scopes;
     }
 
+    // Load google-gax module synchronously if needed
+    if (!gaxInstance) {
+      gaxInstance = require('google-gax') as typeof gax;
+    }
+
     // Choose either gRPC or proto-over-HTTP implementation of google-gax.
-    this._gaxModule = opts.fallback ? gax.fallback : gax;
+    this._gaxModule = opts.fallback ? gaxInstance.fallback : gaxInstance;
 
     // Create a `gaxGrpc` object, with any grpc-specific options sent to the client.
     this._gaxGrpc = new this._gaxModule.GrpcClient(opts);
@@ -146,7 +157,7 @@ export class SubscriberClient {
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;
     }
-    this.iamClient = new IamClient(this._gaxGrpc, opts);
+    this.iamClient = new this._gaxModule.IamClient(this._gaxGrpc, opts);
 
     // Determine the client header string.
     const clientHeader = [`gax/${this._gaxModule.version}`, `gapic/${version}`];
@@ -207,7 +218,7 @@ export class SubscriberClient {
     // Provide descriptors for these.
     this.descriptors.stream = {
       streamingPull: new this._gaxModule.StreamDescriptor(
-        gax.StreamType.BIDI_STREAMING,
+        this._gaxModule.StreamType.BIDI_STREAMING,
         opts.fallback === 'rest'
       ),
     };
@@ -226,7 +237,7 @@ export class SubscriberClient {
     this.innerApiCalls = {};
 
     // Add a warn function to the client constructor so it can be easily tested.
-    this.warn = gax.warn;
+    this.warn = this._gaxModule.warn;
   }
 
   /**
@@ -289,7 +300,9 @@ export class SubscriberClient {
                 setImmediate(() => {
                   stream.emit(
                     'error',
-                    new GoogleError('The client has already been closed.')
+                    new this._gaxModule.GoogleError(
+                      'The client has already been closed.'
+                    )
                   );
                 });
                 return stream;
@@ -582,7 +595,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         name: request.name || '',
       });
     this.initialize();
@@ -664,7 +677,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -749,7 +762,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         'subscription.name': request.subscription!.name || '',
       });
     this.initialize();
@@ -835,7 +848,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -932,7 +945,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -1024,7 +1037,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -1120,7 +1133,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -1214,7 +1227,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -1300,7 +1313,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         snapshot: request.snapshot || '',
       });
     this.initialize();
@@ -1414,7 +1427,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         name: request.name || '',
       });
     this.initialize();
@@ -1503,7 +1516,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         'snapshot.name': request.snapshot!.name || '',
       });
     this.initialize();
@@ -1593,7 +1606,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         snapshot: request.snapshot || '',
       });
     this.initialize();
@@ -1696,7 +1709,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         subscription: request.subscription || '',
       });
     this.initialize();
@@ -1814,7 +1827,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     this.initialize();
@@ -1855,7 +1868,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listSubscriptions'];
@@ -1903,7 +1916,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listSubscriptions'];
@@ -2006,7 +2019,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     this.initialize();
@@ -2047,7 +2060,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listSnapshots'];
@@ -2095,7 +2108,7 @@ export class SubscriberClient {
     options.otherArgs = options.otherArgs || {};
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
-      gax.routingHeader.fromParams({
+      this._gaxModule.routingHeader.fromParams({
         project: request.project || '',
       });
     const defaultCallSettings = this._defaults['listSnapshots'];