puppeteer: slowMo + userDataDir = Error: Protocol error (Browser.close): Target closed.

Tell us about your environment:

• Puppeteer version: 0.13.0
• Platform / OS version: macOS 10.13.1
• URLs (if applicable): https://www.google.com/ (any URLs)

What steps will reproduce the problem?

Please include code that reproduces the issue.

1. use options slowMo and userDataDir together
2. browser.close()

the code:

const path = require('path')
const puppeteer = require('puppeteer')

const run = async () => {
  const browser = await puppeteer.launch({
    headless: false,
    slowMo: 250,
    userDataDir: path.join(process.cwd(), 'state'),
  })
  const page = await browser.newPage()
  await page.goto('https://www.google.com/')
  await browser.close()
}

run()

What is the expected result?

close the browser with no exception

What happens instead?

throw UnhandledPromiseRejectionWarning:

1. Error: Protocol error (Browser.close): Target closed.
2. AssertionError [ERR_ASSERTION]: false == true