diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 71ea972..c6239b6 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
diff --git a/composer.json b/composer.json
index bb99145..264bfeb 100644
--- a/composer.json
+++ b/composer.json
@@ -18,12 +18,16 @@
     },
     "require-dev": {
         "clue/block-react": "^1.1",
-        "phpunit/phpunit": "^9.3 || ^5.7 || ^4.8"
+        "phpunit/phpunit": "^9.6 || ^5.7 || ^4.8.36"
     },
     "autoload": {
-        "psr-4": { "Clue\\React\\Zenity\\": "src/" }
+        "psr-4": {
+            "Clue\\React\\Zenity\\": "src/"
+        }
     },
     "autoload-dev": {
-        "psr-4": { "Clue\\Tests\\React\\Zenity\\": "tests/" }
+        "psr-4": {
+            "Clue\\Tests\\React\\Zenity\\": "tests/"
+        }
     }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 9db1406..4583356 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 9.3+ -->
-<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"
diff --git a/phpunit.xml.legacy b/phpunit.xml.legacy
index 6534d8d..eb1ce33 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>