rails3 validator - has no error message?

Hey

So I can create validations like this:

validates :title, :presence => true, :uniqueness => true, :length => { :maximum => 100 }

BUT I cannot use ":message=>'blah blah'" ... ?

I am stuck with the default "is invalid" error message?

Does anyone have any insite into this?

cheers

Maybe I'm meant to wrap the validation in something?