Mirah build error

gistfile1.txt

> jruby -S rake jar                                                           ~/src/mirah
mkdir -p dist
mkdir -p build
Compiling Ruby sources
Compiling Mirah sources
Parsing...
  org/mirah/class_loader.mirah
  org/mirah/isolated_resource_loader.mirah
  org/mirah/ant/compile.mirah
  duby/lang/compiler/interfaces.duby
  mirah/impl/builtins.mirah
Inferring types...
org/mirah/ant/compile.mirah:27: undefined method `superclass' for Type(error):Mirah::AST::TypeReference
  def initialize
^^^^^^^^^^^^^^^^^
    @src = '.'
^^^^^^^^^^^^^^^
    @target = '.'
^^^^^^^^^^^^^^^^^^
    @classpath = Path.new(getProject)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    @dir = '.'
^^^^^^^^^^^^^^^
    @bytecode = true
^^^^^^^^^^^^^^^^^^^^^
    @verbose = false
^^^^^^^^^^^^^^^^^^^^^
    @jvm_version = '1.6'
^^^^^^^^^^^^^^^^^^^^^^^^^
  end
^^^^^
rake aborted!
undefined method `superclass' for Type(error):Mirah::AST::TypeReference

Tasks: TOP => jar => compile
(See full trace by running task with --trace)