diff --git a/packages/google-cloud-bigquery-datatransfer/src/v1/data_transfer_service_client.ts b/packages/google-cloud-bigquery-datatransfer/src/v1/data_transfer_service_client.ts
index ea155886f15..6906fe3e9a3 100644
--- a/packages/google-cloud-bigquery-datatransfer/src/v1/data_transfer_service_client.ts
+++ b/packages/google-cloud-bigquery-datatransfer/src/v1/data_transfer_service_client.ts
@@ -143,6 +143,8 @@ export class DataTransferServiceClient {
     }
     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}`);