diff --git a/src/v1/big_query_read_client.ts b/src/v1/big_query_read_client.ts
index 83366b79..e0dbfcad 100644
--- a/src/v1/big_query_read_client.ts
+++ b/src/v1/big_query_read_client.ts
@@ -90,8 +90,7 @@ export class BigQueryReadClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
-   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   * @param {boolean} [options.fallback] - Use HTTP/1.1 REST mode.
    *     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
@@ -99,7 +98,7 @@ export class BigQueryReadClient {
    *     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 BigQueryReadClient({fallback: 'rest'}, gax);
+   *     const client = new BigQueryReadClient({fallback: true}, gax);
    *     ```
    */
   constructor(
@@ -162,7 +161,7 @@ export class BigQueryReadClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
-    } else if (opts.fallback === 'rest') {
+    } else {
       clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
@@ -197,7 +196,7 @@ export class BigQueryReadClient {
     this.descriptors.stream = {
       readRows: new this._gaxModule.StreamDescriptor(
         this._gaxModule.StreamType.SERVER_STREAMING,
-        opts.fallback === 'rest'
+        !!opts.fallback
       ),
     };
 
diff --git a/src/v1/big_query_write_client.ts b/src/v1/big_query_write_client.ts
index a2c56ea5..0147a178 100644
--- a/src/v1/big_query_write_client.ts
+++ b/src/v1/big_query_write_client.ts
@@ -93,8 +93,7 @@ export class BigQueryWriteClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
-   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   * @param {boolean} [options.fallback] - Use HTTP/1.1 REST mode.
    *     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
@@ -102,7 +101,7 @@ export class BigQueryWriteClient {
    *     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 BigQueryWriteClient({fallback: 'rest'}, gax);
+   *     const client = new BigQueryWriteClient({fallback: true}, gax);
    *     ```
    */
   constructor(
@@ -165,7 +164,7 @@ export class BigQueryWriteClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
-    } else if (opts.fallback === 'rest') {
+    } else {
       clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
@@ -200,7 +199,7 @@ export class BigQueryWriteClient {
     this.descriptors.stream = {
       appendRows: new this._gaxModule.StreamDescriptor(
         this._gaxModule.StreamType.BIDI_STREAMING,
-        opts.fallback === 'rest'
+        !!opts.fallback
       ),
     };
 
diff --git a/src/v1beta1/big_query_storage_client.ts b/src/v1beta1/big_query_storage_client.ts
index 97a19a7a..afcf3226 100644
--- a/src/v1beta1/big_query_storage_client.ts
+++ b/src/v1beta1/big_query_storage_client.ts
@@ -95,8 +95,7 @@ export class BigQueryStorageClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
-   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   * @param {boolean} [options.fallback] - Use HTTP/1.1 REST mode.
    *     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
@@ -104,7 +103,7 @@ export class BigQueryStorageClient {
    *     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 BigQueryStorageClient({fallback: 'rest'}, gax);
+   *     const client = new BigQueryStorageClient({fallback: true}, gax);
    *     ```
    */
   constructor(
@@ -167,7 +166,7 @@ export class BigQueryStorageClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
-    } else if (opts.fallback === 'rest') {
+    } else {
       clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
@@ -196,7 +195,7 @@ export class BigQueryStorageClient {
     this.descriptors.stream = {
       readRows: new this._gaxModule.StreamDescriptor(
         this._gaxModule.StreamType.SERVER_STREAMING,
-        opts.fallback === 'rest'
+        !!opts.fallback
       ),
     };