diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 2af559af80..e39f175dd6 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -22,7 +22,7 @@ jobs:
 
     strategy:
       matrix:
-        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2']
+        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     name: "Build Phar on PHP: ${{ matrix.php }}"
 
@@ -77,7 +77,7 @@ jobs:
       # - custom_ini: Whether to run with specific custom ini settings to hit very specific
       #   code conditions.
       matrix:
-        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2']
+        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
         custom_ini: [false]
 
         include:
@@ -89,7 +89,7 @@ jobs:
 
     name: "PHP: ${{ matrix.php }} ${{ matrix.custom_ini && ' with custom ini settings' || '' }}"
 
-    continue-on-error: ${{ matrix.php == '8.2' }}
+    continue-on-error: ${{ matrix.php == '8.4' }}
 
     steps:
       - name: Checkout code
@@ -132,11 +132,20 @@ jobs:
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies
+        if: ${{ matrix.php != '8.4' }}
         uses: "ramsey/composer-install@v2"
         with:
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
 
+      # For PHP "nightly", we install with ignore platform reqs.
+      - name: Install Composer dependencies - with ignore platform
+        if: ${{ matrix.php == '8.4' }}
+        uses: "ramsey/composer-install@v2"
+        with:
+          composer-options: --ignore-platform-req=php
+          custom-cache-suffix: $(date -u "+%Y-%m")
+
       # Note: The code style check is run multiple times against every PHP version
       # as it also acts as an integration test.
       - name: 'PHPCS: set the path to PHP'
diff --git a/README.md b/README.md
index c4bc7ead0e..6a2c865c4c 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ PHP_CodeSniffer
 [![License](http://poser.pugx.org/phpcsstandards/php_codesniffer/license)](https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/licence.txt)
 
 ![Minimum PHP Version](https://img.shields.io/packagist/php-v/phpcsstandards/php_codesniffer.svg?maxAge=3600)
-[![Tested on PHP 5.4 to 8.2](https://img.shields.io/badge/tested%20on-PHP%205.4%20|%205.5%20|%205.6%20|%207.0%20|%207.1%20|%207.2%20|%207.3%20|%207.4%20|%208.0%20|%208.1%20|%208.2-brightgreen.svg?maxAge=2419200)](https://github.com/PHPCSStandards/PHP_CodeSniffer/actions/workflows/test.yml)
+[![Tested on PHP 5.4 to 8.3](https://img.shields.io/badge/tested%20on-PHP%205.4%20|%205.5%20|%205.6%20|%207.0%20|%207.1%20|%207.2%20|%207.3%20|%207.4%20|%208.0%20|%208.1%20|%208.2%20|%208.3-brightgreen.svg?maxAge=2419200)](https://github.com/PHPCSStandards/PHP_CodeSniffer/actions/workflows/test.yml)
 
 </div>