diff --git a/composer.json b/composer.json
index 176ce47..a719094 100644
--- a/composer.json
+++ b/composer.json
@@ -30,7 +30,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "~9.0",
-        "vimeo/psalm": "~4.4",
+        "vimeo/psalm": "~5.15",
         "innmind/coding-standard": "~2.0"
     }
 }
diff --git a/psalm.xml b/psalm.xml
index 3240886..510148d 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -2,6 +2,8 @@
 <psalm
     errorLevel="1"
     resolveFromConfigFile="true"
+    findUnusedCode="false"
+    findUnusedBaselineEntry="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
diff --git a/src/Parser/Walker.php b/src/Parser/Walker.php
index 8192b0e..b44ce2a 100644
--- a/src/Parser/Walker.php
+++ b/src/Parser/Walker.php
@@ -69,6 +69,7 @@ public function __invoke(Sequence $lines): Sequence
             })
             ->aggregate(static function(UserAgent|Allow|Disallow|CrawlDelay $a, $b) {
                 if ($a instanceof UserAgent && $b instanceof UserAgent) {
+                    /** @var Sequence<Allow|CrawlDelay|Disallow|UserAgent> */
                     return Sequence::of($a->merge($b));
                 }