diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c6cb342fcd527c27b762f4396cb8403cd5f4df5b..95112f8229e8407d5c3abcebbf3b29d5e9276857 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [2.5, 2.6, 2.7, 3.0]
+        ruby: [2.5, 2.6, 2.7, '3.0']
     steps:
       - uses: actions/checkout@v2
       - name: Set up Ruby
@@ -24,6 +24,6 @@ jobs:
       - name: Install libtidy-dev
         run: sudo apt-get install libtidy-dev
       - name: Install dependencies
-        run: bundle install
+        run: bundle install -j 3
       - name: Run tests
         run: bundle exec rake