diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 598e335..a1a0b1a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -9,11 +9,13 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
+      # Same Ruby series as the GitHub Pages build (https://pages.github.com/versions.json).
+      # Newer runner images only get the latest patch of each series, so keep the series form.
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.1'
+          ruby-version: '3.3'
           bundler-cache: true
 
       - name: Build site