appium: Appium 1.5.0-beta11 start: TypeError: Path must be a string. Received undefined

I’ve installed appium@beta which may fix another issue with Chromedriver. However, after installing it and starting it, I get the following error:

$ appium
TypeError: Path must be a string. Received undefined
    at assertPath (path.js:8:11)
    at Object.win32.resolve (path.js:130:5)
    at Object.<anonymous> (lib/ios-crash-log.js:8:24)
    at Module._compile (module.js:434:26)
    at Object.Module._extensions..js (module.js:452:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at Object.<anonymous> (index.js:1:35)
    at Module._compile (module.js:434:26)
    at Object.Module._extensions..js (module.js:452:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at Object.<anonymous> (lib/driver.js:11:51)
    at Module._compile (module.js:434:26)
    at Object.Module._extensions..js (module.js:452:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)

I’ve tried reinstalling it, but it does not make a difference.