diff --git a/lib/mruby/source.rb b/lib/mruby/source.rb
--- a/lib/mruby/source.rb
+++ b/lib/mruby/source.rb
ROOT = Pathname.new(File.expand_path('../../../',__FILE__))
# Reads a constant defined at version.h
- MRUBY_READ_VERSION_CONSTANT = -> (name) { ROOT.join('include','mruby','version.h').read.match(/^#define #{name} +"?([\w\. ]+)"?$/)[1] }
+ MRUBY_READ_VERSION_CONSTANT = Proc.new { |name| ROOT.join('include','mruby','version.h').read.match(/^#define #{name} +"?([\w\. ]+)"?$/)[1] }
MRUBY_RUBY_VERSION = MRUBY_READ_VERSION_CONSTANT['MRUBY_RUBY_VERSION']
MRUBY_RUBY_ENGINE = MRUBY_READ_VERSION_CONSTANT['MRUBY_RUBY_ENGINE']