Warning messages about mismatched indentation

I have the following program, named hello.rb (you may recognise this - it is on page 15 of the FXRuby book):

require 'fox16' 
app = Fox::FXApp.new 
main = Fox::FXMainWindow.new(app, "Hello World", :width => 200, :height => 100) 
app.create 
main.show(Fox::PLACEMENT_SCREEN) 
app.run

When I run this on Red Hat EnterPrise Linux 5.3, 64-bit, with Ruby 1.9.1, FXRuby 1.16.19 and FOX 1.6.36, I get the following
warnings:

[toll@localhost ~]$ ruby -w hello.rb 
/usr/local/lib/ruby/gems/1.9.1/gems/fxruby-1.6.19/lib/fox16/core.rb:209: warning: mismatched indentations at 'end'
    with 'def' at 207
/usr/local/lib/ruby/gems/1.9.1/gems/fxruby-1.6.19/lib/fox16/core.rb:210: warning: mismatched indentations at 'end'
    with 'class' at 205
[toll@localhost ~]$

The offending code (lines 205-209 of core.rb) is:

class FXScrollArea 
  # Returns a reference to the scroll corner (an FXScrollCorner instance) for this window. 
  def scrollCorner 
    verticalScrollBar.next 
  end 
end

Note that I do not get these warnings with Ruby 1.8.6-111, FXRuby 1.16.16 under Windows XP.

On the Linux system, I installed FOX and Ruby by downloading the tarball sources, and compiling them. The FXRuby was
then installed using gem install fxruby --remote, as shown on page 25 of the FXRuby book.