diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f252e4e0..b74f1beb 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -14,9 +14,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest]
-        ruby: ['2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '3.5', '4.0']
+        os: [ubuntu-24.04]
+        ruby: ['2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '3.5']
         include:
+          - os: ubuntu-latest
+            ruby: '4.0'
           - os: macos-latest
             ruby: '2.6'
           - os: macos-latest
@@ -43,7 +45,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.1'
+          ruby-version: '4.0'
           bundler-cache: true # 'bundle install' and cache
       - run: sudo apt-get update && sudo apt-get install -y valgrind
       - run: bundle exec rake spec:valgrind