diff --git a/.github/workflows/dependency-review.yml b/.github/workflows/dependency-review.yml
index b0dedc4..4e75197 100644
--- a/.github/workflows/dependency-review.yml
+++ b/.github/workflows/dependency-review.yml
@@ -15,6 +15,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 'Checkout Repository'
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: 'Dependency Review'
         uses: actions/dependency-review-action@v3
diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index abdf8ff..225e499 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -16,7 +16,7 @@ jobs:
       matrix:
         node-version: [16.x, 18.x] # https://github.com/nodejs/release#release-schedule
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v3
         with:
@@ -28,7 +28,7 @@ jobs:
     name: ESLint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: npm ci
       - run: npm run lint
         env:
diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 2527c79..7800700 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -16,7 +16,7 @@ jobs:
       matrix:
         php-version: ['7.4', '8.0', '8.1'] # https://www.php.net/supported-versions.php
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Use PHP ${{ matrix.php-version }}
       uses: shivammathur/setup-php@v2
       with:
@@ -33,7 +33,7 @@ jobs:
     name: PHP_CodeSniffer
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: composer install --prefer-dist --no-progress
       - name: Configure PHPCS
         run: ./vendor/squizlabs/php_codesniffer/bin/phpcs --config-set ignore_warnings_on_exit 1
diff --git a/bin/clear-config-cache.php b/bin/clear-config-cache.php
index bc0cdc9..46aef2d 100644
--- a/bin/clear-config-cache.php
+++ b/bin/clear-config-cache.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Script for clearing the configuration cache.
  *
diff --git a/src/App/Handler/ClassHandler.php b/src/App/Handler/ClassHandler.php
index eda74fe..77b2098 100644
--- a/src/App/Handler/ClassHandler.php
+++ b/src/App/Handler/ClassHandler.php
@@ -24,7 +24,7 @@ class ClassHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/LabelHandler.php b/src/App/Handler/LabelHandler.php
index e0bec98..4e04ac6 100644
--- a/src/App/Handler/LabelHandler.php
+++ b/src/App/Handler/LabelHandler.php
@@ -24,7 +24,7 @@ class LabelHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/LayerHandler.php b/src/App/Handler/LayerHandler.php
index 6c263ff..87a4532 100644
--- a/src/App/Handler/LayerHandler.php
+++ b/src/App/Handler/LayerHandler.php
@@ -24,7 +24,7 @@ class LayerHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/MapFileHandler.php b/src/App/Handler/MapFileHandler.php
index b50cd55..317d523 100644
--- a/src/App/Handler/MapFileHandler.php
+++ b/src/App/Handler/MapFileHandler.php
@@ -22,7 +22,7 @@ class MapFileHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/MapHandler.php b/src/App/Handler/MapHandler.php
index b15963f..791c57c 100644
--- a/src/App/Handler/MapHandler.php
+++ b/src/App/Handler/MapHandler.php
@@ -23,7 +23,7 @@ class MapHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/OpenHandler.php b/src/App/Handler/OpenHandler.php
index 39cd2c4..7bfd2f5 100644
--- a/src/App/Handler/OpenHandler.php
+++ b/src/App/Handler/OpenHandler.php
@@ -25,7 +25,7 @@ class OpenHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;
diff --git a/src/App/Handler/StyleHandler.php b/src/App/Handler/StyleHandler.php
index 0681c91..9fa944d 100644
--- a/src/App/Handler/StyleHandler.php
+++ b/src/App/Handler/StyleHandler.php
@@ -24,7 +24,7 @@ class StyleHandler implements RequestHandlerInterface
 
     public function __construct(
         Router\RouterInterface $router,
-        Template\TemplateRendererInterface $template = null,
+        ?Template\TemplateRendererInterface $template = null,
         string $containerName
     ) {
         $this->router = $router;