diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 95633f4..302e582 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,12 +16,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.2', '3.3', '3.4']
-        rails: ['7.1.0', '7.2.0', '8.0.0']
+        ruby: ['3.3', '3.4', '4.0']
+        rails: ['8.0.0', '8.1.0']
         activeadmin: ['3.2.0', '3.3.0', '3.4.0', '3.5.0']
-        exclude:
-          - rails: '8.0.0'
-            activeadmin: '3.2.0'
     env:
       RAILS: ${{ matrix.rails }}
       AA: ${{ matrix.activeadmin }}
@@ -35,7 +32,7 @@ jobs:
         run: bundle exec rspec spec
 
       - name: Generate badge.json
-        if: matrix.ruby == '3.4' && matrix.rails == '8.0.0' && matrix.activeadmin == '3.5.0'
+        if: matrix.ruby == '4.0' && matrix.rails == '8.1.0' && matrix.activeadmin == '3.5.0'
         run: |
           LAST_RUN="coverage/.last_run.json"
           if [ ! -f "$LAST_RUN" ]; then
@@ -53,7 +50,7 @@ jobs:
           echo "{\"schemaVersion\":1,\"label\":\"coverage\",\"message\":\"${PERCENT}%\",\"color\":\"${COLOR}\"}" > badge/badge.json
 
       - name: Upload badge artifact
-        if: matrix.ruby == '3.4' && matrix.rails == '8.0.0' && matrix.activeadmin == '3.5.0'
+        if: matrix.ruby == '4.0' && matrix.rails == '8.1.0' && matrix.activeadmin == '3.5.0'
         uses: actions/upload-artifact@v4
         with:
           name: coverage-badge
diff --git a/active_admin_sidebar.gemspec b/active_admin_sidebar.gemspec
index 3ea52d9..0fee26b 100644
--- a/active_admin_sidebar.gemspec
+++ b/active_admin_sidebar.gemspec
@@ -11,7 +11,7 @@ Gem::Specification.new do |s|
   s.description = %q{extension for activeadmin gem to manage sidebar}
   s.license     = "MIT"
 
-  s.required_ruby_version = '>= 3.1.0'
+  s.required_ruby_version = '>= 3.3'
 
   # Whitelist, not a reject list: a new directory in the repo does not
   # reach consumers until it is named here. The reject form needs a new
diff --git a/tasks/test.rake b/tasks/test.rake
index f46bf45..e72bb7f 100644
--- a/tasks/test.rake
+++ b/tasks/test.rake
@@ -2,10 +2,16 @@ desc "Creates a test rails app for the specs to run against"
 task :setup do
   require 'rails/version'
 
+  # --skip-javascript: the dummy app's own Gemfile is discarded (see
+  # rails_template.rb) and the app boots under this gem's sprockets bundle, so
+  # importmap-rails is never available. Rails 8.1 otherwise generates
+  # `stale_when_importmap_changes` in ApplicationController and the app fails
+  # to boot with a NameError.
   rails_new_opts = %w(
     --skip-turbolinks
     --skip-spring
     --skip-bootsnap
+    --skip-javascript
     -m
     spec/support/rails_template.rb
   )