diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e473cae..e5540f8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,6 +23,7 @@ jobs:
         - macos-latest
         - windows-latest
         ruby:
+        - "4.0"
         - "3.4"
         - "3.3"
         - "3.2"