Recursively count all keys or do something with a hash

hash_recursive_count.rb

def self.counth(thehash,count=0)
  count += thehash.keys.size if thehash.is_a? Hash
  thehash.keys.each do |key|
    if thehash[key].is_a? Hash
      count = counth(thehash[key],count)
    end
  end 
  count
end