diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a885930..a39a166 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,24 +5,22 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        mongoid: [4, 5, 6, 7, 8, HEAD]
+        mongoid: [4, 5, 6, 7, 8, 9 HEAD]
         ruby: [3.2]
         include:
-          - mongoid: 8
-            ruby: 2.7
-          - mongoid: 8
-            ruby: 3.0
-          - mongoid: 8
+          - mongoid: 9
             ruby: 3.1
-          - mongoid: 8
+          - mongoid: 9
             ruby: 3.2
+          - mongoid: 9
+            ruby: 3.3
 
     runs-on: ubuntu-latest
     steps:
       - id: mongodb
         name: Start MongoDB
         uses: mongodb-labs/drivers-evergreen-tools@master
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
diff --git a/Gemfile b/Gemfile
index da0ed0e..08b6b82 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,6 +4,7 @@ gemspec
 
 case version = ENV['MONGOID_VERSION'] || '~> 7.0'
 when 'HEAD' then gem 'mongoid', github: 'mongodb/mongoid'
+when /9/    then gem 'mongoid', '~> 9.0'
 when /8/    then gem 'mongoid', '~> 8.0'
 when /7/    then gem 'mongoid', '~> 7.0'
 when /6/    then gem 'mongoid', '~> 6.0'
diff --git a/mongoid-tree.gemspec b/mongoid-tree.gemspec
index a499749..761837e 100644
--- a/mongoid-tree.gemspec
+++ b/mongoid-tree.gemspec
@@ -12,7 +12,7 @@ Gem::Specification.new do |s|
 
   s.files         = Dir.glob('{lib,spec}/**/*') + %w(LICENSE README.md Rakefile Gemfile)
 
-  s.add_runtime_dependency('mongoid', ['>= 4.0', '< 9'])
+  s.add_runtime_dependency('mongoid', ['>= 4.0', '< 10'])
   s.add_development_dependency('mongoid-compatibility')
   s.add_development_dependency('rake', ['>= 0.9.2'])
   s.add_development_dependency('rspec', ['~> 3.0'])