before_validation to generate permalink if nil not working

If my `title` has content and my `permalink` field is `nil`.. it does not generate the permalink.

 I try from the console many things and it just does not work

ruby 1.9.2 
rails 3.2.3

if I do this to my model it works

```
 before_validation do |record|
    record.generate_permalink! if record.permalink.blank?
 end
```
