diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b2b8f0c..504c2a5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ['3.1', '3.2', '3.3']
+        ruby: ['3.1', '3.2', '3.3', '3.4']
         gemfile:
           - rails_6_1
           - rails_7
diff --git a/Gemfile b/Gemfile
index f78ed55..8690034 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,9 +3,9 @@ source 'https://rubygems.org'
 gemspec
 
 # Ruby 3.4?
-# gem 'base64'
-# gem 'mutex_m'
-# gem 'observer'
+gem 'base64'
+gem 'mutex_m'
+gem 'observer'
 
 gem "rails"
 
diff --git a/merit.gemspec b/merit.gemspec
index 581877d..8644bc1 100644
--- a/merit.gemspec
+++ b/merit.gemspec
@@ -14,6 +14,7 @@ Gem::Specification.new do |s|
 
   s.add_runtime_dependency 'ambry', '~> 1.0.0'
   s.add_runtime_dependency 'zeitwerk'
+  s.add_runtime_dependency 'observer'
 
   s.add_development_dependency 'appraisal'
   s.add_development_dependency 'capybara'