Rails validates_uniqueness_of old data

I've this validation in a model

validates_uniqueness_of :name

I created a new object with a default name and I save it without problems. After, I destroyed it and when I want to save a new object with the same name I have the following error:

ActiveRecord::RecordInvalid: Validation failed: Name has already been taken

I'm using Rails 3.0.20

Any ideas?

Thanks!