diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 38ed72e..c6239b6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,10 +6,14 @@ on:
 
 jobs:
   PHPUnit:
-    runs-on: ubuntu-latest
+    name: PHPUnit (PHP ${{ matrix.php }})
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
         php:
+          - 8.3
+          - 8.2
+          - 8.1
           - 8.0
           - 7.4
           - 7.3
@@ -21,11 +25,11 @@ jobs:
           - 5.4
           - 5.3
     steps:
-      - uses: actions/checkout@v2
-      - name: Setup PHP
-        uses: shivammathur/setup-php@v2
+      - uses: actions/checkout@v4
+      - uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
+          coverage: xdebug
       - run: composer install
       - run: vendor/bin/phpunit --coverage-text
         if: ${{ matrix.php >= 7.3 }}
@@ -34,11 +38,16 @@ jobs:
 
   PHPUnit-hhvm:
     name: PHPUnit (HHVM)
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-22.04
+    continue-on-error: true
     steps:
-      - uses: actions/checkout@v2
-      - uses: azjezz/setup-hhvm@v1
+      - uses: actions/checkout@v4
+      - run: cp "$(which composer)" composer.phar && ./composer.phar self-update --2.2 # downgrade Composer for HHVM
+      - name: Run hhvm composer.phar install
+        uses: docker://hhvm/hhvm:3.30-lts-latest
         with:
-          version: lts-3.30
-      - run: hhvm $(which composer) install
-      - run: hhvm vendor/bin/phpunit
+          args: hhvm composer.phar install
+      - name: Run hhvm vendor/bin/phpunit
+        uses: docker://hhvm/hhvm:3.30-lts-latest
+        with:
+          args: hhvm vendor/bin/phpunit
diff --git a/composer.json b/composer.json
index 636176c..08651d1 100644
--- a/composer.json
+++ b/composer.json
@@ -14,10 +14,14 @@
         "php": ">=5.3"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.3 || ^5.7 || ^4.8.35"
+        "phpunit/phpunit": "^9.6 || ^5.7 || ^4.8.36"
     },
     "autoload": {
-        "files": [ "src/functions.php" ],
-        "psr-4": { "Clue\\Arguments\\": "src/" }
+        "files": [
+            "src/functions.php"
+        ],
+        "psr-4": {
+            "Clue\\Arguments\\": "src/"
+        }
     }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index dc332ca..ee7a557 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,11 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<!-- PHPUnit configuration file with new format for PHPUnit 9.3+ -->
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+<!-- 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/9.6/phpunit.xsd"
          bootstrap="vendor/autoload.php"
+         cacheResult="false"
          colors="true"
-         cacheResult="false">
+         convertDeprecationsToExceptions="true">
     <testsuites>
         <testsuite name="Arguments test suite">
             <directory>./tests/</directory>
@@ -16,4 +17,7 @@
             <directory>./src/</directory>
         </include>
     </coverage>
+    <php>
+        <ini name="error_reporting" value="-1" />
+    </php>
 </phpunit>
diff --git a/phpunit.xml.legacy b/phpunit.xml.legacy
index 8000c04..b854bb7 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 for PHPUnit 9.2 or older -->
+<!-- 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/4.8/phpunit.xsd"
          bootstrap="vendor/autoload.php"
@@ -15,4 +15,7 @@
             <directory>./src/</directory>
         </whitelist>
     </filter>
+    <php>
+        <ini name="error_reporting" value="-1" />
+    </php>
 </phpunit>