diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 302715d..173ae14 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,7 +27,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [3.3, 3.4]
+        ruby: [3.3, 3.4, 4.0]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v6