Shielding issue with copied Request

[TartanLlama]

/// <reference types="@fastly/js-compute" />

import { env } from "fastly:env"; 
import { Shield } from "fastly:shielding";

async function app(event) {
    console.log("FASTLY_SERVICE_VERSION:", env('FASTLY_SERVICE_VERSION') || 'local');
    const req = event.request;
    const newReq = new Request(req.url, {
      body: req.body,
      method: req.method,
    });
    const shield = new Shield('iad-va-us');
    if (shield.runningOn()) {
        return await fetch('https://http-me.fastly.com/anything', { backend: 'httpme' });
    }
    return await fetch(newReq, { backend: shield.encryptedBackend() });
}

addEventListener("fetch", (event) => event.respondWith(app(event)))

This code results in the following error:

Error while running request handler: Requested backend named '**fastly-shield-INTER-IAD-SSL**NRT' does not exist