diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dcec737..de016e3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,20 +2,31 @@ name: CI
 
 on:
   push:
-    branches: main
+    branches: [main]
 
   pull_request:
-    branches: main
+    branches: [main]
 
 jobs:
   test:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ ruby-2.4, ruby-2.5, ruby-2.6, ruby-2.7, ruby-3.0, ruby-3.1, ruby-3.2, jruby-9.2.19, jruby-9.3.0, truffleruby ]
-        os: [ ubuntu-latest, windows-latest ]
+        ruby:
+          [
+            ruby-3.0,
+            ruby-3.1,
+            ruby-3.2,
+            ruby-3.3,
+            ruby-3.4,
+            jruby-9.4.12,
+            jruby-10.0.0,
+            truffleruby,
+          ]
+        os: [ubuntu-latest, windows-latest]
         exclude:
           - { ruby: truffleruby, os: windows-latest }
+          - { ruby: jruby-10.0.0, os: windows-latest }
 
     runs-on: ${{ matrix.os }}
 
@@ -47,8 +58,8 @@ jobs:
 
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.4
-          bundler: 2.3.26
+          ruby-version: 3.0
+          bundler: 2.5.23
 
       - uses: actions/cache@v3
         with:
diff --git a/.rubocop.yml b/.rubocop.yml
index bbae9e4..9538b3b 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,8 +1,8 @@
-require:
+plugins:
   - rubocop-packaging
 
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 3.0
   DisplayCopNames: true
   NewCops: enable
 
@@ -13,6 +13,12 @@ AllCops:
 Gemspec/DuplicatedAssignment:
   Enabled: false
 
+Gemspec/DevelopmentDependencies:
+  Enabled: false
+
+Gemspec/RequireMFA:
+  Enabled: false
+
 #
 # Layout
 #
diff --git a/Gemfile b/Gemfile
index b3c6be7..1fdd4ba 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,6 @@ group :development, :test do
   gem "rake", require: false
   gem "rake-compiler", "~> 1.0", require: false
   gem "rspec", "~> 3.7", require: false
-  gem "rubocop", "~> 1.12.1", require: false
-  gem "rubocop-packaging", "~> 0.5.1", require: false
+  gem "rubocop", "~> 1.75.4", require: false
+  gem "rubocop-packaging", "~> 0.6.0", require: false
 end
diff --git a/README.md b/README.md
index b7eaea1..0c0d7a6 100644
--- a/README.md
+++ b/README.md
@@ -77,8 +77,8 @@ Have questions? Want to suggest a feature or change? Join a discussion group:
 
 **ed25519.rb** is supported on and tested against the following platforms:
 
-* MRI 2.4, 2.5, 2.6, 2.7, 3.0
-* JRuby 9.2.19, 9.3.0
+- MRI 3.0, 3.1, 3.2, 3.3, 3.4
+- JRuby 9.4.12, 10.0.0
 
 ## Installation
 
diff --git a/ed25519.gemspec b/ed25519.gemspec
index be8f9c0..c568088 100644
--- a/ed25519.gemspec
+++ b/ed25519.gemspec
@@ -27,6 +27,6 @@ Gem::Specification.new do |spec|
     spec.extensions = ["ext/ed25519_ref10/extconf.rb"]
   end
 
-  spec.required_ruby_version = ">= 2.4.0"
+  spec.required_ruby_version = ">= 3.0"
   spec.add_development_dependency "bundler"
 end
diff --git a/ext/ed25519_ref10/extconf.rb b/ext/ed25519_ref10/extconf.rb
index 49e469e..ed4c1b9 100644
--- a/ext/ed25519_ref10/extconf.rb
+++ b/ext/ed25519_ref10/extconf.rb
@@ -2,8 +2,6 @@
 
 require "mkmf"
 
-# rubocop:disable Style/GlobalVars
-$CFLAGS << " -Wall -O3 -pedantic -std=c99"
-# rubocop:enable Style/GlobalVars
+append_cflags(["-Wall", "-O3", "-pedantic", "-std=c99"])
 
 create_makefile "ed25519_ref10"