root@ea9d12df0532:/usr/local/bin# webpagetest -V
0.7.1

root@ea9d12df0532:/usr/local/bin# webpagetest --server http://localhost test -l Test -r 1 -y Native www.youtube.com
events.js:291
      throw er; // Unhandled 'error' event
      ^

TypeError [ERR_INVALID_ARG_TYPE]: The "chunk" argument must be of type string or an instance of Buffer. Received undefined
    at validChunk (_stream_writable.js:281:10)
    at WriteStream.Writable.write (_stream_writable.js:316:21)
    at output (/usr/local/lib/node_modules/webpagetest/bin/webpagetest:27:18)
    at Function.formatData (/usr/local/lib/node_modules/webpagetest/bin/webpagetest:68:5)
    at callbackYield (/usr/local/lib/node_modules/webpagetest/lib/webpagetest.js:166:14)
    at WebPageTest.apiCallback (/usr/local/lib/node_modules/webpagetest/lib/webpagetest.js:240:9)
    at IncomingMessage.onEnd (/usr/local/lib/node_modules/webpagetest/lib/webpagetest.js:150:13)
    at IncomingMessage.emit (events.js:326:22)
    at endReadableNT (_stream_readable.js:1241:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21)
Emitted 'error' event on WriteStream instance at:
    at errorOrDestroy (internal/streams/destroy.js:108:12)
    at validChunk (_stream_writable.js:284:5)
    at WriteStream.Writable.write (_stream_writable.js:316:21)
    [... lines matching original stack trace ...]
    at endReadableNT (_stream_readable.js:1241:12) {
  code: 'ERR_INVALID_ARG_TYPE'
}