diff --git a/packages/google-cloud-tasks/src/v2/cloud_tasks_client.ts b/packages/google-cloud-tasks/src/v2/cloud_tasks_client.ts
index 66cebd65aeb..eaddce38323 100644
--- a/packages/google-cloud-tasks/src/v2/cloud_tasks_client.ts
+++ b/packages/google-cloud-tasks/src/v2/cloud_tasks_client.ts
@@ -141,6 +141,8 @@ export class CloudTasksClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/packages/google-cloud-tasks/src/v2beta2/cloud_tasks_client.ts b/packages/google-cloud-tasks/src/v2beta2/cloud_tasks_client.ts
index 258b74f43ab..7f42b0d1232 100644
--- a/packages/google-cloud-tasks/src/v2beta2/cloud_tasks_client.ts
+++ b/packages/google-cloud-tasks/src/v2beta2/cloud_tasks_client.ts
@@ -141,6 +141,8 @@ export class CloudTasksClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/packages/google-cloud-tasks/src/v2beta3/cloud_tasks_client.ts b/packages/google-cloud-tasks/src/v2beta3/cloud_tasks_client.ts
index 0fefb5c728c..3ca0997056a 100644
--- a/packages/google-cloud-tasks/src/v2beta3/cloud_tasks_client.ts
+++ b/packages/google-cloud-tasks/src/v2beta3/cloud_tasks_client.ts
@@ -141,6 +141,8 @@ export class CloudTasksClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);