diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 40fdcf9..a398ff9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,7 @@ jobs:
     strategy:
       matrix:
         php:
+          - 8.3
           - 8.2
           - 8.1
           - 8.0
@@ -19,7 +20,7 @@ jobs:
           - 7.2
           - 7.1
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
@@ -37,6 +38,7 @@ jobs:
     strategy:
       matrix:
         php:
+          - 8.3
           - 8.2
           - 8.1
           - 8.0
@@ -44,7 +46,7 @@ jobs:
           - 7.3
           - 7.2
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
diff --git a/composer.json b/composer.json
index cca3d03..5d1e277 100644
--- a/composer.json
+++ b/composer.json
@@ -28,8 +28,8 @@
         "php": ">=7.1.0"
     },
     "require-dev": {
-        "phpstan/phpstan": "1.10.34 || 1.4.10",
-        "phpunit/phpunit": "^9.5 || ^7.5"
+        "phpstan/phpstan": "1.10.39 || 1.4.10",
+        "phpunit/phpunit": "^9.6 || ^7.5"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index bba7c90..33ea968 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<!-- PHPUnit configuration file with new format for PHPUnit 9.5+ -->
+<!-- PHPUnit configuration file with new format for PHPUnit 9.6+ -->
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.5/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
          bootstrap="vendor/autoload.php"
          cacheResult="false"
          colors="true"
@@ -24,7 +24,7 @@
     <php>
         <ini name="error_reporting" value="-1" />
         <!-- Evaluate assertions, requires running with "php -d zend.assertions=1 vendor/bin/phpunit" -->
-        <!-- <ini name="zend.assertions=1" value="1" /> -->
+        <!-- <ini name="zend.assertions" value="1" /> -->
         <ini name="assert.active" value="1" />
         <ini name="assert.exception" value="1" />
         <ini name="assert.bail" value="0" />
diff --git a/phpunit.xml.legacy b/phpunit.xml.legacy
index 4bdf771..0dacab1 100644
--- a/phpunit.xml.legacy
+++ b/phpunit.xml.legacy
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<!-- PHPUnit configuration file with old format before PHPUnit 9 -->
+<!-- PHPUnit configuration file with old format for legacy PHPUnit -->
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/7.5/phpunit.xsd"
          bootstrap="vendor/autoload.php"
@@ -22,7 +22,7 @@
     <php>
         <ini name="error_reporting" value="-1" />
         <!-- Evaluate assertions, requires running with "php -d zend.assertions=1 vendor/bin/phpunit" -->
-        <!-- <ini name="zend.assertions=1" value="1" /> -->
+        <!-- <ini name="zend.assertions" value="1" /> -->
         <ini name="assert.active" value="1" />
         <ini name="assert.exception" value="1" />
         <ini name="assert.bail" value="0" />