diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 3efbc12..3a48f7d 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -31,6 +31,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version:
+          - '4.0'
           - 3.4
           - 3.3
           - 3.2