testem: Testem process exits (times out?) after 10s with code 1, no error

It seems to happen when my webpack process takes longer than 10s to build, I have this in my config:

{
  "framework": "tap",
  "launch_in_dev": ["PhantomJS"],
  "launch_in_ci": ["PhantomJS"],
  "src_files": ["tests/bundle.js"],
  "serve_files": ["tests/bundle.js"],
  "on_start": {
    "command": "npm run build:test:watch",
    "wait_for_text": "[built]"
  },
  "on_exit": {
    "command": "rm tests/bundle.js"
  }
}

The build:test:watch script basically does webpack --define process.env.NODE_ENV='\"test\"' tests/index.js tests/bundle.js --watch

Is there some timeout in testem that will kill the process if it doesn’t see the wait_for_text after 10s?