diff --git a/phpBB/composer.json b/phpBB/composer.json
index b402534c13..64657daab5 100644
--- a/phpBB/composer.json
+++ b/phpBB/composer.json
@@ -43,8 +43,8 @@
 		"s9e/text-formatter": "^2.0",
 		"symfony/config": "^6.3",
 		"symfony/console": "^6.3",
-		"symfony/debug": "~4.4",
 		"symfony/dependency-injection": "^6.3",
+		"symfony/error-handler": "^6.3",
 		"symfony/event-dispatcher": "^6.3",
 		"symfony/filesystem": "^6.3",
 		"symfony/finder": "^6.3",
diff --git a/phpBB/composer.lock b/phpBB/composer.lock
index 675f5d42d7..73b27c5c52 100644
--- a/phpBB/composer.lock
+++ b/phpBB/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "845ee61ff0e24697c187704eecc6a51f",
+    "content-hash": "0c305d521f2db3eec61dcef5b8359047",
     "packages": [
         {
             "name": "bantu/ini-get-wrapper",
@@ -2847,75 +2847,6 @@
             ],
             "time": "2023-08-16T10:10:12+00:00"
         },
-        {
-            "name": "symfony/debug",
-            "version": "v4.4.44",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/symfony/debug.git",
-                "reference": "1a692492190773c5310bc7877cb590c04c2f05be"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/symfony/debug/zipball/1a692492190773c5310bc7877cb590c04c2f05be",
-                "reference": "1a692492190773c5310bc7877cb590c04c2f05be",
-                "shasum": ""
-            },
-            "require": {
-                "php": ">=7.1.3",
-                "psr/log": "^1|^2|^3"
-            },
-            "conflict": {
-                "symfony/http-kernel": "<3.4"
-            },
-            "require-dev": {
-                "symfony/http-kernel": "^3.4|^4.0|^5.0"
-            },
-            "type": "library",
-            "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\Debug\\": ""
-                },
-                "exclude-from-classmap": [
-                    "/Tests/"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                },
-                {
-                    "name": "Symfony Community",
-                    "homepage": "https://symfony.com/contributors"
-                }
-            ],
-            "description": "Provides tools to ease debugging PHP code",
-            "homepage": "https://symfony.com",
-            "support": {
-                "source": "https://github.com/symfony/debug/tree/v4.4.44"
-            },
-            "funding": [
-                {
-                    "url": "https://symfony.com/sponsor",
-                    "type": "custom"
-                },
-                {
-                    "url": "https://github.com/fabpot",
-                    "type": "github"
-                },
-                {
-                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
-                    "type": "tidelift"
-                }
-            ],
-            "abandoned": "symfony/error-handler",
-            "time": "2022-07-28T16:29:46+00:00"
-        },
         {
             "name": "symfony/dependency-injection",
             "version": "v6.3.4",
diff --git a/phpBB/phpbb/debug/debug.php b/phpBB/phpbb/debug/debug.php
index c5ffada2e5..eacb28c25c 100644
--- a/phpBB/phpbb/debug/debug.php
+++ b/phpBB/phpbb/debug/debug.php
@@ -13,14 +13,13 @@
 
 namespace phpbb\debug;
 
-use Symfony\Component\Debug\BufferingLogger;
-use Symfony\Component\Debug\DebugClassLoader;
-use Symfony\Component\Debug\ExceptionHandler;
+use Symfony\Component\ErrorHandler\BufferingLogger;
+use Symfony\Component\ErrorHandler\ErrorHandler;
 
 /**
  * Registers all the debug tools.
 
- * @see Symfony\Component\Debug\Debug
+ * @see \Symfony\Component\ErrorHandler\Debug
  */
 class debug
 {
@@ -34,10 +33,10 @@ class debug
 	 * If the Symfony ClassLoader component is available, a special
 	 * class loader is also registered.
 	 *
-	 * @param int  $errorReportingLevel The level of error reporting you want
-	 * @param bool $displayErrors       Whether to display errors (for development) or just log them (for production)
+	 * @param int|null $errorReportingLevel The level of error reporting you want
+	 * @param bool $displayErrors Whether to display errors (for development) or just log them (for production)
 	 */
-	public static function enable($errorReportingLevel = null, $displayErrors = true)
+	public static function enable(?int $errorReportingLevel = null, bool $displayErrors = true): void
 	{
 		if (static::$enabled)
 		{
@@ -58,7 +57,7 @@ class debug
 		if ('cli' !== php_sapi_name())
 		{
 			ini_set('display_errors', 0);
-			ExceptionHandler::register();
+			ErrorHandler::register();
 		}
 		else if ($displayErrors && (!ini_get('log_errors') || ini_get('error_log')))
 		{
@@ -75,6 +74,6 @@ class debug
 			error_handler::register()->throwAt(0, true);
 		}
 
-		DebugClassLoader::enable();
+		Debug::enable();
 	}
 }
diff --git a/phpBB/phpbb/debug/error_handler.php b/phpBB/phpbb/debug/error_handler.php
index f2b00e6365..2356045b4d 100644
--- a/phpBB/phpbb/debug/error_handler.php
+++ b/phpBB/phpbb/debug/error_handler.php
@@ -13,7 +13,7 @@
 
 namespace phpbb\debug;
 
-use Symfony\Component\Debug\ErrorHandler;
+use Symfony\Component\ErrorHandler\ErrorHandler;
 
 /**
  * @psalm-suppress InvalidExtendClass
@@ -23,7 +23,7 @@ class error_handler extends ErrorHandler
 	/**
 	 * @psalm-suppress MethodSignatureMismatch
 	 */
-	public function handleError($type, $message, $file, $line)
+	public function handleError(int $type, string $message, string $file, int $line): bool
 	{
 		if ($type === E_USER_WARNING || $type === E_USER_NOTICE)
 		{