foo.rb

class Foo
  def bar
    "wtf?"
  end
  protected :bar

  def invoke_bar
    public_send(:bar)
  end
end

puts Foo.public_send(:bar) rescue puts "error; this seems normal"

puts Foo.new.invoke_bar

# The last statement outputs "wtf?" on:
# * 1.9.3p194
# * 1.9.3p327

# The last statement raises a NoMethodError on:
# * JRuby 1.7.0
# * rubinius 2.0.0dev 2279857e
#
# I /expected/ the NoMethodError behavior

Shouldn't line 12 be Foo.new.public_send(:bar)? You haven't defined a class method bar.

+1 to myron, though it does work as you'd expect even if you do that (NoMethodError exception).

BTW, this was a bug in Rubinius until several months ago too: jfirebaugh/rubinius@b3a4533