diff --git a/phpBB/config/default/container/services_event.yml b/phpBB/config/default/container/services_event.yml
index 8a55b933ac..5696275e64 100644
--- a/phpBB/config/default/container/services_event.yml
+++ b/phpBB/config/default/container/services_event.yml
@@ -9,6 +9,7 @@ services:
         arguments:
             - '@template'
             - '@language'
+            - '%debug.exceptions%'
         tags:
             - { name: kernel.event_subscriber }
 
diff --git a/phpBB/language/en/common.php b/phpBB/language/en/common.php
index af9f8fe187..d7a1ce8e71 100644
--- a/phpBB/language/en/common.php
+++ b/phpBB/language/en/common.php
@@ -556,6 +556,7 @@ $lang = array_merge($lang, array(
 	),
 	'OPTIONS'					=> 'Options',
 
+	'PAGE_NOT_FOUND'		=> 'The requested page could not be found.',
 	'PAGE_OF'				=> 'Page <strong>%1$d</strong> of <strong>%2$d</strong>',
 	'PAGE_TITLE_NUMBER'		=> 'Page %s',
 	'PASSWORD'				=> 'Password',
diff --git a/phpBB/phpbb/event/kernel_exception_subscriber.php b/phpBB/phpbb/event/kernel_exception_subscriber.php
index b7a54f2608..373e59b0c8 100644
--- a/phpBB/phpbb/event/kernel_exception_subscriber.php
+++ b/phpBB/phpbb/event/kernel_exception_subscriber.php
@@ -16,12 +16,20 @@ namespace phpbb\event;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\HttpKernel\KernelEvents;
 use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
 use Symfony\Component\HttpFoundation\Response;
 
 class kernel_exception_subscriber implements EventSubscriberInterface
 {
+	/**
+	 * Set to true to show full exception messages
+	 *
+	 * @var bool
+	 */
+	protected $debug;
+
 	/**
 	* Template object
 	*
@@ -44,9 +52,11 @@ class kernel_exception_subscriber implements EventSubscriberInterface
 	*
 	* @param \phpbb\template\template	$template	Template object
 	* @param \phpbb\language\language	$language	Language object
+	* @param bool						$debug		Set to true to show full exception messages
 	*/
-	public function __construct(\phpbb\template\template $template, \phpbb\language\language $language)
+	public function __construct(\phpbb\template\template $template, \phpbb\language\language $language, $debug = false)
 	{
+		$this->debug = $debug || defined('DEBUG');
 		$this->template = $template;
 		$this->language = $language;
 		$this->type_caster = new \phpbb\request\type_cast_helper();
@@ -69,6 +79,10 @@ class kernel_exception_subscriber implements EventSubscriberInterface
 		{
 			$message = $this->language->lang_array($message, $exception->get_parameters());
 		}
+		else if (!$this->debug && $exception instanceof NotFoundHttpException)
+		{
+			$message = $this->language->lang('PAGE_NOT_FOUND');
+		}
 
 		// Show <strong> text in bold
 		$message = preg_replace('#&lt;(/?strong)&gt;#i', '<$1>', $message);
@@ -99,7 +113,7 @@ class kernel_exception_subscriber implements EventSubscriberInterface
 				$data['message'] = $message;
 			}
 
-			if (defined('DEBUG'))
+			if ($this->debug)
 			{
 				$data['trace'] = $exception->getTrace();
 			}