diff --git a/Rakefile b/Rakefile
index a317c65..b5f2189 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,8 +1,15 @@
 require "bundler/gem_tasks"
 require "rake/testtask"
 require "shellwords"
+require "rake/extensiontask"
+
+extask = Rake::ExtensionTask.new("date") do |ext|
+  ext.name = "date_core"
+  ext.lib_dir.sub!(%r[(?=/|\z)], "/#{RUBY_VERSION}/#{ext.platform}")
+end
 
 Rake::TestTask.new(:test) do |t|
+  t.libs << extask.lib_dir
   t.libs << "test/lib"
   t.ruby_opts << "-rhelper"
   t.test_files = FileList['test/**/test_*.rb']
@@ -20,12 +27,6 @@ file "ext/date/zonetab.h" => "ext/date/zonetab.list" do |t|
      hdr, chdir: dir)
 end
 
-require 'rake/extensiontask'
-Rake::ExtensionTask.new("date") do |ext|
-  ext.name = "date_core"
-  ext.lib_dir.sub!(%r[(?=/|\z)], "/#{RUBY_VERSION}/#{ext.platform}")
-end
-
 task :sync_tool do
   require 'fileutils'
   FileUtils.cp "../ruby/tool/lib/core_assertions.rb", "./test/lib"