diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d987dd0..e9f5076 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['2.7', '3.0', '3.1', '3.2']
+        ruby: ['2.7', '3.0', '3.1', '3.2', '3.3']
         gemfile:
           - gemfiles/rails_5_2.gemfile
           - gemfiles/rails_6_0.gemfile
@@ -18,6 +18,8 @@ jobs:
           - gemfiles/rails_7_2.gemfile
           - gemfiles/rails_8_0.gemfile
         exclude:
+          - ruby: '3.3'
+            gemfile: gemfiles/rails_5_2.gemfile
           - ruby: '3.2'
             gemfile: gemfiles/rails_5_2.gemfile
           - ruby: '3.1'
diff --git a/Appraisals b/Appraisals
index d313e16..b7cb3a5 100644
--- a/Appraisals
+++ b/Appraisals
@@ -10,6 +10,7 @@ appraise 'rails-6-0' do
   gem 'activejob', '~> 6.0.0'
   gem 'activerecord', '~> 6.0.0'
   gem 'sqlite3', '~> 1.4'
+  gem 'concurrent-ruby', '1.3.4'
 end
 
 appraise 'rails-6-1' do
@@ -17,6 +18,7 @@ appraise 'rails-6-1' do
   gem 'activejob', '~> 6.1.0'
   gem 'activerecord', '~> 6.1.0'
   gem 'sqlite3', '~> 1.4'
+  gem 'concurrent-ruby', '1.3.4'
 end
 
 appraise 'rails-7-0' do
@@ -24,6 +26,7 @@ appraise 'rails-7-0' do
   gem 'activejob', '~> 7.0.0'
   gem 'activerecord', '~> 7.0.0'
   gem 'sqlite3', '~> 1.4'
+  gem 'concurrent-ruby', '1.3.4'
 end
 
 appraise 'rails-7-1' do
diff --git a/gemfiles/rails_6_0.gemfile b/gemfiles/rails_6_0.gemfile
index 6e2572f..e9494d1 100644
--- a/gemfiles/rails_6_0.gemfile
+++ b/gemfiles/rails_6_0.gemfile
@@ -14,5 +14,6 @@ gem "rspec"
 gem "timecop"
 gem "zeitwerk"
 gem "sqlite3", "~> 1.4"
+gem "concurrent-ruby", "1.3.4"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_6_1.gemfile b/gemfiles/rails_6_1.gemfile
index 938c6a7..6cbed42 100644
--- a/gemfiles/rails_6_1.gemfile
+++ b/gemfiles/rails_6_1.gemfile
@@ -14,5 +14,6 @@ gem "rspec"
 gem "timecop"
 gem "zeitwerk"
 gem "sqlite3", "~> 1.4"
+gem "concurrent-ruby", "1.3.4"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_7_0.gemfile b/gemfiles/rails_7_0.gemfile
index c995e3f..00dd1b7 100644
--- a/gemfiles/rails_7_0.gemfile
+++ b/gemfiles/rails_7_0.gemfile
@@ -14,5 +14,6 @@ gem "rspec"
 gem "timecop"
 gem "zeitwerk"
 gem "sqlite3", "~> 1.4"
+gem "concurrent-ruby", "1.3.4"
 
 gemspec path: "../"