diff --git a/Gemfile b/Gemfile
index 38529b462..e79d75416 100644
--- a/Gemfile
+++ b/Gemfile
@@ -10,7 +10,7 @@ gem 'bump', require: false
 gem 'prism'
 gem 'rake'
 gem 'rspec'
-gem 'rubocop', github: 'rubocop/rubocop'
+gem 'rubocop', path: '/Users/koic/src/github.com/rubocop/rubocop'
 gem 'rubocop-rspec', '~> 3.0.0'
 gem 'simplecov'
 gem 'test-queue'
diff --git a/spec/project_spec.rb b/spec/project_spec.rb
index 342f226fd..e5596a7b7 100644
--- a/spec/project_spec.rb
+++ b/spec/project_spec.rb
@@ -22,8 +22,8 @@
         start_with_subject = description.match(/\AThis cop (?<verb>.+?) .*/)
         suggestion = start_with_subject[:verb]&.capitalize if start_with_subject
         suggestion ||= 'a verb'
-        expect(start_with_subject).to(
-          be_nil, "`Description` for `#{name}` should be started with `#{suggestion}` instead of `This cop ...`."
+        expect(start_with_subject.nil?).to(
+          be(true), "`Description` for `#{name}` should be started with `#{suggestion}` instead of `This cop ...`."
         )
       end
     end