diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 99d6021..6a31f64 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -15,7 +15,7 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@0dafeac902942906541bc140009cdbf32665b601 # ruby/setup-ruby@v1 see https://github.com/ruby/setup-ruby/tree/v1
       with:
-        ruby-version: '3.3'
+        ruby-version: '4.0'
     - name: Install dependencies
       run: bundle install
     - name: Run RuboCop against BASE..HEAD changes
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6a71d56..ca8d067 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,13 +8,14 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version:
-          - '3.2'
           - '3.3'
           - '3.4'
+          - '4.0'
         gemfile:
           - gemfiles/Gemfile.rails71
           - gemfiles/Gemfile.rails72
           - gemfiles/Gemfile.rails80
+          - gemfiles/Gemfile.rails81
         exclude:
           # rails 8.0 requires ruby >= 3.2
           # https://www.fastruby.io/blog/ruby/rails/versions/compatibility-table.html
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 57c672d..b79d7c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## [Unreleased]
 ### Fixed
 * Support Ruby 3.4. Drop support for Rails 7.0, Ruby 3.1
+* Support Ruby 4.0, Rails 8.1. Drop support for Ruby 3.2
 
 ## 0.4.3 / 2024-11-19
 ### Added
diff --git a/gemfiles/Gemfile.rails81 b/gemfiles/Gemfile.rails81
new file mode 100644
index 0000000..9706eb2
--- /dev/null
+++ b/gemfiles/Gemfile.rails81
@@ -0,0 +1,6 @@
+source 'https://rubygems.org'
+
+gemspec path: '..'
+
+gem 'activerecord',  '~> 8.1.0'
+gem 'activesupport', '~> 8.1.0'
diff --git a/ndr_browser_timings.gemspec b/ndr_browser_timings.gemspec
index b382642..7640f7e 100644
--- a/ndr_browser_timings.gemspec
+++ b/ndr_browser_timings.gemspec
@@ -16,9 +16,9 @@ Gem::Specification.new do |spec|
   spec.files       = `git ls-files -z`.split("\x0").
                      select { |f| gem_files.include?(f.split('/')[0]) }
 
-  spec.add_dependency 'rails', '>= 7.1', '< 8.1'
+  spec.add_dependency 'rails', '>= 7.1', '< 8.2'
 
-  spec.required_ruby_version = '>= 3.2.0'
+  spec.required_ruby_version = '>= 3.3'
 
   spec.add_development_dependency 'mocha'
   spec.add_development_dependency 'ndr_dev_support', '>= 6.0'
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 5ab0611..bd3206d 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -17,12 +17,11 @@
 Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
 # Load fixtures from the engine
-if ActiveSupport::TestCase.respond_to?(:fixture_path=)
-  ActiveSupport::TestCase.fixture_path = File.expand_path('fixtures', __dir__)
-  ActionDispatch::IntegrationTest.fixture_path = ActiveSupport::TestCase.fixture_path
-  ActiveSupport::TestCase.file_fixture_path = ActiveSupport::TestCase.fixture_path + '/files'
-  ActiveSupport::TestCase.fixtures :all
-end
+fixtures_dir = File.expand_path('fixtures', __dir__)
+ActiveSupport::TestCase.fixture_paths << fixtures_dir # Rails >= 7.1
+ActionDispatch::IntegrationTest.fixture_paths << fixtures_dir
+ActiveSupport::TestCase.file_fixture_path = "#{fixtures_dir}/files"
+ActiveSupport::TestCase.fixtures :all
 
 ActiveSupport::TestCase.class_eval do
   def capture_recordings