ffmpeg-worker-mp4: Requested output format 'h264' is not a suitable output format

Question

I'd like to grab the video stream of a selected mp4 to decode it later:

  async onFileSelected(event: Event) {
    const file: File = (event as any).target.files[0];
    console.log(file);

    const sourceBuffer = await file.arrayBuffer();

    const worker = new Worker('ffmpeg-worker-mp4.js');
    let output;
    worker.onmessage = function (e) {
      const msg = e.data;
      switch (msg.type) {
        case 'ready':
          worker.postMessage({
            type: 'run',
            MEMFS: [
              { name: 'test.mp4', data: sourceBuffer },
              { name: 'test.h264', data: output },
            ],
            arguments: [
              '-i',
              'test.mp4',
              '-c:v',
              'copy',
              '-bsf:v',
              'h264_mp4toannexb',
              '-an',
              '-f',
              'h264',
              'test.h264',
            ],
          });
          break;
        case 'stdout':
          console.log(msg.data);
          break;
        case 'stderr':
          console.log(msg.data);
          break;
        case 'done':
          console.log(msg.data);
          console.log(output);
          break;
      }
    };
  }

I receive the following errors:

Requested output format 'h264' is not a suitable output format test.h264: Invalid argument

I tested the same command using my command line and it works fine. What am I missing?