inheritance.rb

class TheUppermostClass
  def initialize(one, two, three, four)
  end
end

class TheInheritingClass < TheUppermostClass
  def initialize(one, two, three)
    super(one, two, three, 'four')
  end
end

class TheInheritingClass
  # You'll have to do the `alias_method` dance because `super` doesn't work 
  # when overriding methods, only when you want to call to the superclass.
  
  alias_method :__initialize_before_override, :initialize
  private :__initialize_before_override

  def initialize(*args)
    __initialize_before_override(*args)
  end
end

TheInheritingClass.new('one', 'two', 'three')

That looks like a pretty good workaround. Thanks very much!

I kind of assumed super would call the method you're overriding in the current class if any, otherwise the one in the superclass. Don't know if that would make sense, though.