diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c9a5cbc..eb3b7ce 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,6 +20,7 @@ jobs:
           - macos-latest
           - windows-latest
         ruby:
+          - 4.0
           - 3.4
           - 3.3
           - 3.2