diff --git a/Rakefile b/Rakefile
index 797929ad..d4416d95 100644
--- a/Rakefile
+++ b/Rakefile
@@ -16,18 +16,6 @@ RDoc::Task.new(:docs) do |rd|
   rd.options << "-t #{title}"
 end
 
-require 'rake/testtask'
-
-Rake::TestTask.new(:test) do |t|
-  t.libs << "test/lib"
-  t.ruby_opts << "-rhelper"
-  t.test_files = FileList["test/**/test_*.rb"]
-  if RUBY_VERSION >= "2.6"
-    t.ruby_opts << "--enable-frozen-string-literal"
-    t.ruby_opts << "--debug=frozen-string-literal" if RUBY_ENGINE != "truffleruby"
-  end
-end
-
 def java?
   /java/ === RUBY_PLATFORM
 end
@@ -39,12 +27,16 @@ file 'lib/racc/parser-text.rb' => ['lib/racc/parser.rb', __FILE__] do |t|
   source = 'lib/racc/parser.rb'
 
   text = File.read(source)
+  text.sub!(/\A# *frozen[-_]string[-_]literal:.*\n/, '')
   text.gsub!(/^require '(.*)'$/) do
-    %[unless $".find {|p| p.end_with?('/#$1.rb')}\n$".push "\#{__dir__}/#$1.rb"\n#{File.read("lib/#{$1}.rb")}\nend\n]
+    lib = $1
+    code = File.read("lib/#{lib}.rb")
+    code.sub!(/\A(?:#.*\n)+/, '')
+    %[unless $".find {|p| p.end_with?('/#{lib}.rb')}\n$".push "\#{__dir__}/#{lib}.rb"\n#{code}\nend\n]
   rescue
     $&
   end
-  open(t.name, 'wb') { |io|
+  File.open(t.name, 'wb') { |io|
     io.write(<<-eorb)
 module Racc
   PARSER_TEXT = <<'__end_of_file__'
@@ -58,10 +50,10 @@ end
 if jruby?
   # JRUBY
   require "rake/javaextensiontask"
-  Rake::JavaExtensionTask.new("cparse") do |ext|
+  extask = Rake::JavaExtensionTask.new("cparse") do |ext|
     jruby_home = RbConfig::CONFIG['prefix']
-    ext.lib_dir = File.join 'lib', 'racc'
-    ext.ext_dir = File.join 'ext', 'racc'
+    ext.lib_dir = 'lib/java/racc'
+    ext.ext_dir = 'ext/racc'
     # source/target jvm
     ext.source_version = '1.8'
     ext.target_version = '1.8'
@@ -69,19 +61,31 @@ if jruby?
     ext.classpath = jars.map { |x| File.expand_path x }.join( ':' )
     ext.name = 'cparse-jruby'
   end
-
-  task :compile => ['lib/racc/parser-text.rb']
 else
   # MRI
   require "rake/extensiontask"
-  Rake::ExtensionTask.new "cparse" do |ext|
-    ext.lib_dir = File.join 'lib', 'racc'
-    ext.ext_dir = File.join 'ext', 'racc', 'cparse'
+  extask = Rake::ExtensionTask.new "cparse" do |ext|
+    ext.lib_dir << "/#{RUBY_VERSION}/#{ext.platform}/racc"
+    ext.ext_dir = 'ext/racc/cparse'
   end
-
-  task :compile => 'lib/racc/parser-text.rb'
 end
 
+task :compile => ['lib/racc/parser-text.rb']
+
 task :build => "lib/racc/parser-text.rb"
 
 task :test => :compile
+
+require 'rake/testtask'
+
+Rake::TestTask.new(:test) do |t|
+  ENV["RUBYOPT"] = "-I" + [extask.lib_dir, "test/lib"].join(File::PATH_SEPARATOR)
+  t.libs << extask.lib_dir
+  t.libs << "test/lib"
+  t.ruby_opts << "-rhelper"
+  t.test_files = FileList["test/**/test_*.rb"]
+  if RUBY_VERSION >= "2.6"
+    t.ruby_opts << "--enable-frozen-string-literal"
+    t.ruby_opts << "--debug=frozen-string-literal" if RUBY_ENGINE != "truffleruby"
+  end
+end
diff --git a/lib/racc/info.rb b/lib/racc/info.rb
index b0fc9055..a6bd249c 100644
--- a/lib/racc/info.rb
+++ b/lib/racc/info.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 #--
 #
 #
diff --git a/lib/racc/parser.rb b/lib/racc/parser.rb
index ab1e5bcc..c4c74fae 100644
--- a/lib/racc/parser.rb
+++ b/lib/racc/parser.rb
@@ -1,4 +1,4 @@
-# frozen_string_literal: false
+# frozen_string_literal: true
 #--
 # Copyright (c) 1999-2006 Minero Aoki
 #