diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e4d0050..4eb5937 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['7.1', '7.2', '7.3', '7.4', '8.0']
+        php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     steps:
       - name: Checkout code
diff --git a/src/LoggerPlugin.php b/src/LoggerPlugin.php
index ce0b67a..0ef7be9 100644
--- a/src/LoggerPlugin.php
+++ b/src/LoggerPlugin.php
@@ -23,7 +23,7 @@ final class LoggerPlugin implements Plugin
 
     private $formatter;
 
-    public function __construct(LoggerInterface $logger, Formatter $formatter = null)
+    public function __construct(LoggerInterface $logger, ?Formatter $formatter = null)
     {
         $this->logger = $logger;
         $this->formatter = $formatter ?: new SimpleFormatter();