diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f89898b..7258677 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
@@ -24,7 +25,7 @@ jobs:
           - 5.4
           - 5.3
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
@@ -47,7 +48,7 @@ jobs:
     runs-on: ubuntu-22.04
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cp "$(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
diff --git a/composer.json b/composer.json
index 01a4b85..8723a6e 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,7 @@
         "react/stream": "^1.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5 || ^5.7 || ^4.8.35",
+        "phpunit/phpunit": "^9.6 || ^5.7 || ^4.8.36",
         "react/event-loop": "^1.2"
     },
     "autoload": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 106750f..44299b3 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"