diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9a82177..31d6de6 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -32,7 +32,7 @@ jobs:
     - name: OpenSSL test
       run: ruby -ropen-uri -e 'puts open(%{https://rubygems.org/}) { |f| f.read(1024) }'
     - name: C extension test
-      run: gem install json --no-document
+      run: gem install json:2.2.0 --no-document
     - name: Bundler version
       run: bundle --version
     - name: Bundler test
diff --git a/Gemfile b/Gemfile
index bc93e59..319828b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,4 +2,4 @@
 source 'https://rubygems.org'
 
 gem "path"
-gem "json"
+gem "json", "2.2.0"