diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 53679f37..55c0cb83 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ jobs:
     name: build (${{ matrix.ruby }}/${{ matrix.test_mode }})
     strategy:
       matrix:
-        ruby: [ '3.3', '3.2', '3.1', '3.0' ]
+        ruby: [ '3.4', '3.3', '3.2', '3.1', '3.0' ]
         test_mode: [ rack, gem ]
     runs-on: ubuntu-latest
     services:
@@ -21,12 +21,6 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-    - run: |
-        gem install bundler --no-document -v '2.4.22'
-      if: matrix.ruby == '2.7'
-    - run: |
-        gem update --system --no-document
-      if: matrix.ruby != '2.7'
     - name: Install dependencies
       run: |
         echo 'gemspec' > Gemfile.local
diff --git a/tdiary.gemspec b/tdiary.gemspec
index 55be1652..c5d4f707 100644
--- a/tdiary.gemspec
+++ b/tdiary.gemspec
@@ -40,6 +40,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'hikidoc'
   spec.add_dependency 'mail'
   spec.add_dependency 'rack'
+  spec.add_dependency 'nkf'
   spec.add_dependency 'rake'
   spec.add_dependency 'thor'
   spec.add_dependency 'rexml'