diff --git a/.github/workflows/gem-publish.yml b/.github/workflows/gem-publish.yml
index 0a1672a..f146639 100644
--- a/.github/workflows/gem-publish.yml
+++ b/.github/workflows/gem-publish.yml
@@ -17,7 +17,7 @@ jobs:
 
     strategy:
       matrix:
-        ruby-version: [3.2, 3.3, 3.4]
+        ruby-version: [3.2, 3.3, 3.4, 4.0]
     steps:
       - uses: actions/checkout@v6
       - name: Set up Ruby
diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 498fd9a..bdf4c67 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby-version: [3.2, 3.3, 3.4]
+        ruby-version: [3.2, 3.3, 3.4, 4.0]
 
     steps:
     - uses: actions/checkout@v6
diff --git a/Gemfile b/Gemfile
index 7f4f5e9..4a659b9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,4 +2,7 @@
 
 source 'https://rubygems.org'
 
+# Explicitly require these gems for Ruby 4.0 compatibility
+gem 'minitest', '>= 5.0'
+
 gemspec
diff --git a/docs/TRUSTED_PUBLISHING.md b/docs/TRUSTED_PUBLISHING.md
index f42ba52..8e6c619 100644
--- a/docs/TRUSTED_PUBLISHING.md
+++ b/docs/TRUSTED_PUBLISHING.md
@@ -5,7 +5,7 @@ This repository now uses RubyGems trusted publishing via GitHub Actions OIDC tok
 ## How it works
 
 1. **Automated Publishing**: When code is pushed to the `master` branch, the workflow automatically:
-   - Runs the full test suite across multiple Ruby versions (3.1, 3.2, 3.3, 3.4)
+   - Runs the full test suite across multiple Ruby versions (3.1, 3.2, 3.3, 3.4, 4.0)
    - Builds the gem if tests pass
    - Publishes to RubyGems using OIDC token authentication
    - Creates a GitHub release
diff --git a/lib/twiglet/version.rb b/lib/twiglet/version.rb
index 3fff3ed..7aa6673 100644
--- a/lib/twiglet/version.rb
+++ b/lib/twiglet/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Twiglet
-  VERSION = '3.15.0'
+  VERSION = '3.16.0'
 end
diff --git a/twiglet.gemspec b/twiglet.gemspec
index d83e839..0e02af2 100644
--- a/twiglet.gemspec
+++ b/twiglet.gemspec
@@ -25,12 +25,14 @@ Gem::Specification.new do |gem|
   gem.files                 = Dir.glob(['lib/**/*', 'LICENSE', 'README.md']).reject { |f| File.directory?(f) }
 
   gem.require_paths         = ['lib']
-  gem.required_ruby_version = ['>= 3.2 ', '< 3.5']
+  gem.required_ruby_version = ['>= 3.2 ', '< 4.1']
 
   gem.license               = 'MIT'
 
   gem.add_dependency 'json-schema'
-  gem.add_development_dependency 'minitest'
+  gem.add_development_dependency 'benchmark'
+  gem.add_development_dependency 'cgi'
+  gem.add_development_dependency 'minitest', '>= 5.0'
   gem.add_development_dependency 'minitest-mock'
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'rbs'