The following program causes segmentation fault for me with the latest macruby trunk: class A def somemethod puts "A::somemethod" end end module B def somemethod super puts "B::somemethod" end end module C def somemethod super puts "C::somemethod" end end class D < A include B include C def somemethod super puts "D::somemethod" end end obj = D.new obj.somemethod Thanks to http://weblog.rubyonrails.org/2009/8/31/three-reasons-love-responder I just found that modules can be chained via super like that, so I immediately went to check it out, and in MRI 1.8 it works fine. I wanted to see it in 1.9, so I checked with macruby and it caused segmentation fault. I recompiled latest macruby trunk and it's still happening. As stated in the README.rdoc I'm using llvm trunk at revision 72741. Is it llvm or macruby bug? Oddly, under gdb it just freezes, can't even see any stack trace. :-/