diff --git a/.github/workflows/reline.yml b/.github/workflows/reline.yml
index a6c2730c19..45582fb8ea 100644
--- a/.github/workflows/reline.yml
+++ b/.github/workflows/reline.yml
@@ -103,7 +103,7 @@ jobs:
           make
           sudo make install
       - name: Install dependencies
-        run: bundle install
+        run: bundle install && bundle add tsort
       - name: Install reline
         run: rake install
       - name: Download ruby/irb
@@ -112,7 +112,7 @@ jobs:
       - name: Run irb test
         working-directory: ./irb
         run: |
-          bundle install
+          bundle install && bundle add tsort
           bundle exec rake test
       - name: Run irb yamatanooroti test
         working-directory: ./irb
diff --git a/Gemfile b/Gemfile
index c439329c52..f3d94938ae 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,6 +13,7 @@ gem 'bundler'
 gem 'rdoc'
 gem 'rake'
 gem 'test-unit'
+gem 'tsort'
 
 # Only used in ci to run readline-ext test using Reline as Readline
 gem 'readline'