diff --git a/unf_ext.gemspec b/unf_ext.gemspec
index abe0cd2..3e7db6c 100644
--- a/unf_ext.gemspec
+++ b/unf_ext.gemspec
@@ -12,23 +12,6 @@ Gem::Specification.new do |gem|
   gem.homepage      = "https://github.com/knu/ruby-unf_ext"
   gem.licenses      = ["MIT"]
 
-  gem.files         = `git ls-files`.split($/)
-  gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
-  gem.test_files    = gem.files.grep(%r{^(test|spec|features)/}).grep(%r{/test_[^/]+\.rb$})
+  gem.files         = ["lib/unf_ext.rb", "lib/unf_ext/version.rb", "lib/unf_ext.so"]
   gem.require_paths = ["lib"]
-  gem.extensions    = ["ext/unf_ext/extconf.rb"]
-
-  gem.extra_rdoc_files = [
-    "LICENSE.txt",
-    "README.md"
-  ]
-
-  gem.required_ruby_version = '>= 2.2'
-
-  gem.add_development_dependency("rake", [">= 0.9.2.2"])
-  gem.add_development_dependency("test-unit")
-  gem.add_development_dependency("rdoc", ["> 2.4.2"])
-  gem.add_development_dependency("bundler", [">= 1.2"])
-  gem.add_development_dependency("rake-compiler", [">= 1.1.1"])
-  gem.add_development_dependency("rake-compiler-dock", [">= 1.2.1"])
 end