diff --git a/.github/workflows/gouteur.yml b/.github/workflows/gouteur.yml
index fee6259..bf73e1e 100644
--- a/.github/workflows/gouteur.yml
+++ b/.github/workflows/gouteur.yml
@@ -11,7 +11,7 @@ jobs:
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.7
+          ruby-version: 3.3
       - name: Prepare
         run: |
           bundle install --jobs 4
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 45f1ac7..68147c8 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -13,7 +13,7 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.7
+        ruby-version: 3.3
     - name: Cache gems
       uses: actions/cache@v1
       with:
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d35cb67..eb5763e 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        ruby: [ '2.3', '2.7', '3.0', '3.1', 'ruby-head', 'jruby-head' ]
+        ruby: [ '2.4', '2.7', '3.0', '3.1', '3.2', '3.3', 'ruby-head', 'jruby-head' ]
 
     steps:
       - uses: actions/checkout@v2
@@ -25,4 +25,4 @@ jobs:
       - name: Test with Rake
         run: bundle exec rake
       - uses: codecov/codecov-action@v3
-        if: matrix.ruby == '2.7'
+        if: matrix.ruby == '3.2'
diff --git a/Gemfile b/Gemfile
index dc31acc..c22a3cf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,14 +7,15 @@ gemspec
 
 gem 'benchmark-ips', '~> 2.7'
 gem 'get_process_mem', '~> 0.2.3'
-gem 'rake', '~> 13.0'
+gem 'rake', '~> 13.1'
 gem 'rake-compiler', '~> 1.1'
 gem 'range_compressor', '~> 1.0'
 gem 'regexp_parser', '~> 2.9'
 gem 'regexp_property_values', '~> 1.5'
 gem 'rspec', '~> 3.8'
-if RUBY_VERSION.to_f >= 2.7
+gem 'warning', '~> 1.3'
+if RUBY_VERSION.to_f >= 3.0
   gem 'gouteur', '~> 1.0.0'
   gem 'rubocop', '~> 1.59'
-  gem 'simplecov-cobertura'
+  gem 'simplecov-cobertura', require: false
 end
diff --git a/spec/character_set/ractor_compatibility_spec.rb b/spec/character_set/ractor_compatibility_spec.rb
index 86f0b25..0ab86ce 100644
--- a/spec/character_set/ractor_compatibility_spec.rb
+++ b/spec/character_set/ractor_compatibility_spec.rb
@@ -1,4 +1,6 @@
-describe CharacterSet, if: defined?(Ractor) do
+# skip ractor test when evaluating coverage
+# https://github.com/simplecov-ruby/simplecov/issues/1058
+describe CharacterSet, if: defined?(Ractor) && !defined?(SimpleCov) do
   it 'can be used with Ractor' do
     shared_instance = CharacterSet[97, 98, 99].freeze
     CharacterSet.const_set('RactorTestFrozen', shared_instance)
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 909439e..eccc6ea 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,16 +1,16 @@
-if ENV['CI'] && RUBY_VERSION.start_with?('2.7')
+require 'bundler/setup'
+Dir[File.join(__dir__, 'support', '*.rb')].sort.each { |file| require file }
+
+if ENV['CI'] && RUBY_VERSION.start_with?('3.2')
   require 'simplecov'
   require 'simplecov-cobertura'
   SimpleCov.formatter = SimpleCov::Formatter::CoberturaFormatter
   SimpleCov.start
 end
 
-require 'bundler/setup'
 require 'character_set'
 require 'character_set/pure'
 
-Dir[File.join(__dir__, 'support', '*.rb')].sort.each { |file| require file }
-
 RSpec.configure do |config|
   # Enable flags like --only-failures and --next-failure
   config.example_status_persistence_file_path = ".rspec_status"
diff --git a/spec/support/flush_default_ractor_warning.rb b/spec/support/flush_default_ractor_warning.rb
deleted file mode 100644
index 49d2091..0000000
--- a/spec/support/flush_default_ractor_warning.rb
+++ /dev/null
@@ -1,4 +0,0 @@
-previous_verbose = $VERBOSE
-$VERBOSE = nil
-defined?(Ractor) && Ractor.new { nil }
-$VERBOSE = previous_verbose
diff --git a/spec/support/silence_default_ractor_warning.rb b/spec/support/silence_default_ractor_warning.rb
new file mode 100644
index 0000000..e59c5d5
--- /dev/null
+++ b/spec/support/silence_default_ractor_warning.rb
@@ -0,0 +1,2 @@
+require 'warning'
+Warning.ignore(/Ractor is experimental/)