diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index fe1de0aa..efcb4cfb 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -46,7 +46,7 @@ jobs:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.4.8
+          ruby-version: 4.0.1
       - run: bundle install
       - name: Standard
         run: bundle exec rake standard
diff --git a/.ruby-version b/.ruby-version
index 7921bd0c..1454f6ed 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.8
+4.0.1
diff --git a/.tool-versions b/.tool-versions
index 58766197..6e03b218 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1 +1 @@
-ruby 3.4.8
+ruby 4.0.1