diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 902c2dcb..8ae50122 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -1,29 +1,46 @@
 name: Ruby Build
 on: [push, pull_request]
 jobs:
-  build:
+  jruby_build:
+    name: JRuby (${{ matrix.ruby }})
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: [2.4.0, 2.6.0, 3.0.0, jruby-9.2.18.0]
+        ruby: [jruby-9.2.18]
     steps:
-      - run: echo "The job was automatically triggered by a ${{ github.event_name }} event."
-      - run: echo "This job is now running on a ${{ runner.os }} server hosted by GitHub!"
-      - run: echo "The name of your branch is ${{ github.ref }} and your repository is ${{ github.repository }}."
       - name: Check out repository code
         uses: actions/checkout@v2
-      - run: echo "The ${{ github.repository }} repository has been cloned to the runner."
-      - run: echo "The workflow is now ready to test your code on the runner."
       - name: List files in the repository
         run: |
           ls ${{ github.workspace }}
-      - uses: actions/setup-java@v2
+      - name: Set up Java
+        uses: actions/setup-java@v2
         with:
           distribution: 'adopt'
           java-version: '11'
-      - uses: ruby/setup-ruby@v1
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: true
-      - name: exec rake
+      - name: Run tests
+        run: bundle exec rake
+  mri_build:
+    name: Ruby (${{ matrix.ruby }})
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: [2.6, 2.7, 3.0]
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v2
+      - name: List files in the repository
+        run: |
+          ls ${{ github.workspace }}
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - name: Run tests
         run: bundle exec rake
diff --git a/Gemfile b/Gemfile
index 1d210903..c79d5637 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,9 +1,26 @@
 source 'https://rubygems.org'
 
-if RUBY_PLATFORM == 'java'
-  gem 'warbler'
-end
+gem 'warbler', platforms: :jruby
+
+# FIXME:
+#
+# There's an issue in 1.12.5 that causes XHTML elements to be generated badly,
+# causing Gollum's test suite to fail.[1] The issue has been fixed upstream,
+# but we're still waiting for a new Nokogiri point release.
+#
+# However, 1.12.5 is a security patch, so we don't want end users to use an
+# older version of Nokogiri. But this is safe to do in our CI environment.
+#
+# Once there's a new Nokogiri release, we can remove this dependency and JRuby
+# CI should pass normally again.
+#
+# Note that Nokogiri 1.11+ does not support Ruby v2.4.x anymore. So to make our
+# current CI workflows pass, we should only try to install this version of
+# Nokogiri for newer Ruby versions.
+#
+# [1]: https://github.com/gollum/gollum/issues/1779
+gem 'nokogiri', '1.12.4' unless RUBY_VERSION.include? '2.4'
 
 gemspec
 
-gem 'rake', '~> 13.0'
\ No newline at end of file
+gem 'rake', '~> 13.0'
diff --git a/gollum.gemspec b/gollum.gemspec
index 4fcb20fc..a0449f65 100644
--- a/gollum.gemspec
+++ b/gollum.gemspec
@@ -44,7 +44,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rack-test', '~> 0.6.3'
   s.add_development_dependency 'shoulda', '~> 3.6.0'
   s.add_development_dependency 'minitest-reporters', '~> 1.3.6'
-  s.add_development_dependency 'twitter_cldr', '~> 3.2.0'
   s.add_development_dependency 'mocha', '~> 1.8.0'
   s.add_development_dependency 'test-unit', '~> 3.3.0'
 
diff --git a/test/helper.rb b/test/helper.rb
index 17c0ec92..8bf4c7dc 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -6,7 +6,6 @@ require 'mocha/setup'
 require 'fileutils'
 require 'minitest/reporters'
 require 'minitest/spec'
-require 'twitter_cldr'
 require 'tmpdir'
 
 # Silence locale validation warning
diff --git a/test/test_app.rb b/test/test_app.rb
index 906ec8a8..48836f83 100644
--- a/test/test_app.rb
+++ b/test/test_app.rb
@@ -39,31 +39,29 @@ context "Frontend" do
     assert_match /<pre><code>one\ntwo\nthree\nfour\n<\/code><\/pre>\n/m, last_response.body
   end
 
-  def nfd utf8
-    TwitterCldr::Normalization.normalize(utf8, using: :nfd)
-  end
-  
   test 'mathjax assets are served' do
     get '/gollum/assets/mathjax/MathJax.js'
     assert last_response.ok?
   end
 
   test "UTF-8 headers href preserved" do
-    page = 'utfh1'
-    text = nfd('한글')
+    page_content = <<~TEXT
+      ## 한글
 
-    # don't use h1 or it will be promoted to replace file name
-    # which doesn't generate a normal header link
-    @wiki.write_page(page, :markdown, '## ' + text,
-                     { :name => 'user1', :email => 'user1' });
+      Test page "utfh1" content.
+    TEXT
 
-    get page
-    expected = "<h2 class=\"editable\"><a class=\"anchor\" (href|id)=\"(#)?#{text}\" (href|id)=\"(#)?#{text}\"></a>#{text}</h2>"
-    actual   = nfd(last_response.body)
+    @wiki.write_page('utfh1',
+                     :markdown,
+                     page_content,
+                     {name: 'user1', email: 'user1'})
 
-    assert_match /#{expected}/, actual
+    get 'utfh1'
+    expected = "<h2 class=\"editable\"><a class=\"anchor\" (href|id)=\"(#)?한글\" (href|id)=\"(#)?한글\"></a>한글</h2>"
+
+    assert_match /#{expected}/, last_response.body
   end
-  
+
   test 'rss feed' do
     channel_title = <<EOF
 <title>Gollum Wiki Latest Changes</title>