diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f6e24ed..882a26a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,6 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
+          - '4.0'
           - '3.4'
           - '3.3'
           - '3.2'