Groovy Encapsulation - Say What?

I'm reading Groovy Recipes by Scott Davis and find this troubling:

class Book3{
private String title
private String getTitle(){}
private void setTitle(title){}
}
def b3 = new Book3()
b3.@title = "Groovy Recipes"
println b3.@title
===> Groovy Recipes

In Groovy, private attributes can be modified, even if you use private setters. That's not cool. I'm hoping there's some way to enforce encapsulation, but it's not looking good right now.