class User
include Mongoid::Document
validates_uniqueness_of :email , :case_sensitive => false
end

User.create!(:email => 'test@test.com')
User.create!(:email => 'TEST@TEST.COM')

Both users are saved. This should not be the case. If we change line 29 of uniquness.rb to be

criteria = @klass.where(attribute => (options[:case_sensistive] ? value : Regexp.new(value, Regexp::IGNORECASE)))

and change line 27 to be

criteria = criteria.where(attribute =>( options[:case_sensistive] ? value : Regexp.new(value, Regexp::IGNORECASE)), :_id =>

{'$ne' => document._id})

That should do the trick.

It could also be done with:

criteria = @klass.where(attribute => Regexp.new(value, !options[:case_sensistive]) )

and
criteria = criteria.where(attribute => Regexp.new(value, !options[:case_sensistive]), :_id => {'$ne' => document._id}

)