diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
new file mode 100644
index 0000000..c3f10e1
--- /dev/null
+++ b/.devcontainer/devcontainer.json
@@ -0,0 +1,14 @@
+{
+  "name": "microcms-ruby-sdk",
+  "image": "ghcr.io/rails/devcontainer/images/ruby:4.0.5",
+  "postCreateCommand": "bin/setup",
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "Shopify.ruby-lsp",
+        "rebornix.Ruby"
+      ]
+    }
+  },
+  "remoteUser": "vscode"
+}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 19f96af..a2426e6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,12 +10,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
 
       - name: Setup Ruby and install gems
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@0dafeac902942906541bc140009cdbf32665b601 # v1.315.0
         with:
-          ruby-version: 2.7
           bundler-cache: true
 
       - name: Run linters
@@ -26,13 +27,15 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: [2.6, 2.7, 3.0]
+        ruby-version: [2.6, 2.7, 3.4, 4.0]
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+      with:
+        persist-credentials: false
 
     - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@0dafeac902942906541bc140009cdbf32665b601 # v1.315.0
       with:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 176561a..fbd653d 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -14,11 +14,11 @@ jobs:
       packages: write
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+    - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       with:
-        ruby-version: 2.6.x
+        persist-credentials: false
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@0dafeac902942906541bc140009cdbf32665b601 # v1.315.0
 
     - name: Publish to RubyGems
       run: |
diff --git a/.rubocop.yml b/.rubocop.yml
index 2fbb3c9..6c669e2 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -9,3 +9,13 @@ Metrics/BlockLength:
 Style/OpenStructUse:
   Exclude:
     - 'spec/**/*'
+
+Style/RedundantConstantBase:
+  Exclude:
+    - 'spec/**/*'
+
+Style/ZeroLengthPredicate:
+  Enabled: false
+
+Style/SafeNavigation:
+  Enabled: false
diff --git a/.ruby-version b/.ruby-version
index 37c2961..7636e75 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.7.2
+4.0.5
diff --git a/lib/microcms.rb b/lib/microcms.rb
index a603d59..9d4afb8 100644
--- a/lib/microcms.rb
+++ b/lib/microcms.rb
@@ -5,6 +5,7 @@
 require 'uri'
 require 'json'
 require 'forwardable'
+require 'ostruct'
 
 # MicroCMS
 module MicroCMS
diff --git a/microcms.gemspec b/microcms.gemspec
index 9fc6652..67b0ad2 100644
--- a/microcms.gemspec
+++ b/microcms.gemspec
@@ -26,4 +26,6 @@ Gem::Specification.new do |spec|
   spec.bindir        = 'exe'
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
+
+  spec.add_dependency 'ostruct'
 end