Fibonacci with Ruby's .reduce

reduce_fibonacci.rb

# find the nth value of the Fibonacci sequence
def fibonacci(nth)
  counter = 1
  current_arr = [0, 1]
  until counter == nth - 1
    next_val = current_arr.reduce(0) {|sum, number| sum + number }
    current_arr = [current_arr.last, next_val]
    counter += 1
  end
  current_arr.last
end