diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 14a1162..fd17f3e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,7 +21,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
       - run: bundle exec rake style
 
@@ -56,7 +56,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
       # Catches a hand-edit of a generated file, and a spec change that was
       # vendored without regenerating against it.
@@ -69,7 +69,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
       - run: bundle exec steep check
 
@@ -80,7 +80,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
       - run: bundle exec rake doc_coverage
 
diff --git a/.github/workflows/integration.yml b/.github/workflows/integration.yml
index f8f434a..20e54db 100644
--- a/.github/workflows/integration.yml
+++ b/.github/workflows/integration.yml
@@ -22,7 +22,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
 
       # ubuntu-latest runners ship with Docker already running, so there is
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 51c8811..38e4eea 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.6"
           bundler-cache: true
 
       - name: Verify before publishing