diff --git a/.github/workflows/code-style.yml b/.github/workflows/code-style.yml
index b106cd3..66a1b3d 100644
--- a/.github/workflows/code-style.yml
+++ b/.github/workflows/code-style.yml
@@ -6,15 +6,15 @@ on:
 
 jobs:
   phpcs:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: Install PHP
       uses: shivammathur/setup-php@v2
       with:
         coverage: none
-        php-version: "8.0"
+        php-version: "8.3"
         ini-values: memory_limit=-1
         tools: phpcs, cs2pr
     - name: Run PHP Code Sniffer
diff --git a/.github/workflows/static-analysis.yml b/.github/workflows/static-analysis.yml
index 3b5da94..6a87b5e 100644
--- a/.github/workflows/static-analysis.yml
+++ b/.github/workflows/static-analysis.yml
@@ -7,18 +7,18 @@ on:
 jobs:
   phpstan:
     name: phpstan
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: Install PHP
       uses: shivammathur/setup-php@v2
       with:
-        php-version: "8.1"
+        php-version: "8.3"
         ini-values: memory_limit=-1
         tools: composer:v2
     - name: Cache dependencies
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: |
           ~/.composer/cache
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index fa2121a..887606a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -7,15 +7,16 @@ on:
 jobs:
   phpunit:
     name: phpunit
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         php-version:
         - "8.1"
         - "8.2"
+        - "8.3"
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: Install PHP
       uses: shivammathur/setup-php@v2
       with:
@@ -24,7 +25,7 @@ jobs:
         ini-values: memory_limit=-1
         tools: composer:v2
     - name: Cache dependencies
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: |
           ~/.composer/cache
@@ -39,7 +40,7 @@ jobs:
       run: make test-coveralls
 
     - name: Upload code coverage
-      if: ${{ matrix.php-version == '8.1' }}
+      if: ${{ matrix.php-version == '8.3' }}
       env:
         COVERALLS_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
diff --git a/Dockerfile b/Dockerfile
index 2ceb1c9..ec9e615 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 ARG PHP_VERSION
-FROM php:${PHP_VERSION}-cli-buster
+FROM php:${PHP_VERSION}-cli-bookworm
 
 RUN apt-get update && \
 	apt-get install -y autoconf pkg-config && \
diff --git a/Makefile b/Makefile
index 861862f..c7784d4 100644
--- a/Makefile
+++ b/Makefile
@@ -34,7 +34,12 @@ test-container-81:
 
 .PHONY: test-container-82
 test-container-82:
-	@-docker-compose run --rm app81 bash
+	@-docker-compose run --rm app82 bash
+	@docker-compose down -v
+
+.PHONY: test-container-83
+test-container-83:
+	@-docker-compose run --rm app83 bash
 	@docker-compose down -v
 
 .PHONY: lint
diff --git a/composer.json b/composer.json
index 611b550..5f77deb 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
     },
     "require-dev": {
         "phpstan/phpstan": "^1.10",
-        "phpunit/phpunit": "^10.3",
+        "phpunit/phpunit": "^10.5",
         "symfony/config": "^6.3"
     },
     "autoload": {
diff --git a/docker-compose.yaml b/docker-compose.yaml
index 0ab45d8..fd6946e 100644
--- a/docker-compose.yaml
+++ b/docker-compose.yaml
@@ -21,3 +21,13 @@ services:
     volumes:
     - .:/app:delegated
     - ~/.composer:/root/.composer:delegated
+  app83:
+    build:
+      context: .
+      args:
+        PHP_VERSION: "8.3"
+    environment:
+      PHP_IDE_CONFIG: "serverName=symfony-di-proxy"
+    volumes:
+    - .:/app:delegated
+    - ~/.composer:/root/.composer:delegated
diff --git a/lib/MethodRenderer.php b/lib/MethodRenderer.php
index 4411a8b..e7f8992 100644
--- a/lib/MethodRenderer.php
+++ b/lib/MethodRenderer.php
@@ -106,9 +106,13 @@ function (ReflectionParameter $parameter) {
     private function renderType(ReflectionType $type): string
     {
         if ($type instanceof ReflectionUnionType) {
-            return implode('|', array_map(function (ReflectionNamedType $namedType) {
-                return $namedType->getName();
-            }, $type->getTypes()));
+            return implode(
+                '|',
+                array_map(
+                    fn(ReflectionNamedType $namedType) => $namedType->getName(), // @phpstan-ignore-line
+                    $type->getTypes()
+                )
+            );
         }
 
         assert($type instanceof ReflectionNamedType);
diff --git a/phpunit.xml b/phpunit.xml
index f83be0c..55562d3 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.3/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
          colors="true"
          bootstrap="tests/bootstrap.php"
 >