Virtus: empty string on Integer is empty string. By design or bug?

virtus_blank_string.rb

require 'virtus'

class Record
  include Virtus
  attribute :count, Integer
end

record = Record.new
record.count = ''

puts "Expecting nil:"
p record.count # -> ''

# This is problematic with form input that is either an empty string
# or an integer (a database id). Besides, '' isn't an integer.