Cannot call job for instance method?

Greetings, can someone give me some help? I'm trying to use job for a instance method, as it's described here but...

Anyway, I have a method like this:

Method PrepareInstance(path)
{
  set ..Tool = ##class(Tool).%New(path)
  do $System.Event.Signal($zparent)
}

That is being called like this:

Method TestPurge() As %Status
{
  job ..PrepareInstance(..GetTestDirectory("../fixtures/_/dummy-project"))::10
  set msg = $System.Event.Wait("",10)
}

But it fails because:

<METHOD DOES NOT EXIST>zTestPurge+1^UnitTest.Tool.1 *PrepareInstance

Am I missing something or is that a bug? The method surely exists and the job is also being created inside another instance method.

Thanks in advance.