SteamGuard event not providing callback

[Rodrigo]

I have been receiving an error: "callback is not a function". I believe it has something to do with this implementation: 
 

watchSteamGuard(profileId) {
  const client = this.client(profileId) // SteamUser Client
  const sharedCode = this.sharedCode(profileId)
  client.on(‘steamGuard’, function (_, callback, lastCodeWrong) {
    if (lastCodeWrong) {
      setTimeout(function () {
        callback(SteamTotp.getAuthCode(sharedCode))
      }, 30000)
    }
  })
}

I am on version 4.18. Have no idea what might be causing the problem. Any insight would be greatly appreciated.