Irb not working in stable snapshot

Look what I have here:

zeus:~ # ruby -v
ruby 1.8.4 (2006-02-12) [i686-linux]

zeus:~ # irb -v
irb 0.9.5(05/04/13)

zeus:~ # irb
/usr/local/lib/ruby/1.8/irb/workspace.rb:52: undefined method
`irb_binding’ for main:Object (NoMethodError)

The line in question is

 @binding = eval("def irb_binding; binding; end; irb_binding",
           __LINE__ - 3)

which worked in the Christmas release I am running on the other system.