diff --git a/README.md b/README.md
index 49cbda3..0589f83 100644
--- a/README.md
+++ b/README.md
@@ -24,11 +24,12 @@ default:
 
 ### Config values
 
-| config  | default       | Environment    | Description                   |
-| ------- | ------------- | -------------- | ----------------------------- |
-| verbose | false         | none           | Enables/disables verbose mode |
-| rootDir | /var/www/html | BEHAT_HOST     | Specifies http root dir       |
-| host    | localhost     | BEHAT_ROOT_DIR | Host domain or IP             |
+| config  | default       | Environment    | Description                                        |
+| ------- | ------------- | -------------- | -------------------------------------------------- |
+| verbose | false         | none           | Enables/disables verbose mode                      |
+| rootDir | /var/www/html | BEHAT_HOST     | Specifies http root dir                            |
+| host    | localhost     | BEHAT_ROOT_DIR | Host domain or IP                                  |
+| runAs   |               | BEHAT_RUN_AS   | The username to be used to run the built-in server |
 
 You can also use `-v` option to enable verbose mode. Example
 ```bash
@@ -78,4 +79,4 @@ class FeatureContext implements Context
         }
     }
 }
-```
\ No newline at end of file
+```
diff --git a/psalm.xml b/psalm.xml
index 4e9226b..065d4b3 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -1,6 +1,9 @@
 <?xml version="1.0"?>
 <psalm
+    errorBaseline="tests/psalm-baseline.xml"
     errorLevel="2"
+    findUnusedBaselineEntry="true"
+    findUnusedCode="false"
     resolveFromConfigFile="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
diff --git a/src/RunServerListener.php b/src/RunServerListener.php
index f5d6dfa..2972e2b 100644
--- a/src/RunServerListener.php
+++ b/src/RunServerListener.php
@@ -36,12 +36,14 @@ class RunServerListener implements EventSubscriberInterface
     private static int $port = 0;
     private ?int $verbose = null;
     private string $rootDir;
+    private string $runAs = '';
     private static self $instance;
 
-    public function __construct(?int $verbose, string $rootDir, string $host)
+    public function __construct(?int $verbose, string $rootDir, string $host, string $runAs)
     {
         $this->verbose = $verbose;
         $this->rootDir = $rootDir;
+        $this->runAs = $runAs;
         self::$host = $host;
         self::$instance = $this;
     }
@@ -79,6 +81,10 @@ public function start(): void
 
         $cmd = 'php -S ' . self::$host .':' . self::$port . ' -t ' . $script;
 
+        if ($this->runAs) {
+            $cmd = 'runuser -u ' . $this->runAs . ' -- ' . $cmd;
+        }
+
         if (is_numeric($this->verbose)) {
             $verbose = '';
         } else {
@@ -195,8 +201,10 @@ public function getPort()
      * Let the OS find an open port for you.
      *
      * @return int
+     *
+     * @psalm-return int<1, max>
      */
-    private function findOpenPort()
+    private function findOpenPort(): int
     {
         $sock = socket_create(AF_INET, SOCK_STREAM, 0);
 
diff --git a/src/Server.php b/src/Server.php
index d977eaa..be19fa1 100644
--- a/src/Server.php
+++ b/src/Server.php
@@ -72,6 +72,10 @@ public function configure(ArrayNodeDefinition $builder): void
                     ->info('Host domain or IP')
                     ->defaultValue('localhost')
                 ->end()
+                ->scalarNode('runAs')
+                    ->info('The username to be used to run the built-in server')
+                    ->defaultValue('')
+                ->end()
             ->end()
         ;
     }
@@ -88,9 +92,10 @@ public function load(ContainerBuilder $container, array $config): void
             }
         }
         $host = $this->getHost($config);
+        $runAs = $this->getRunAs($config);
         $definition = (new Definition('PhpBuiltin\RunServerListener'))
             ->addTag('event_dispatcher.subscriber')
-            ->setArguments([$verbose, $rootDir, $host])
+            ->setArguments([$verbose, $rootDir, $host, $runAs])
         ;
 
         $container->setDefinition(self::ID . '.listener', $definition);
@@ -105,6 +110,15 @@ private function getHost(array $config): string
         return (string) $host;
     }
 
+    private function getRunAs(array $config): string
+    {
+        $runAs = getenv('BEHAT_RUN_AS');
+        if ($runAs === false) {
+            $runAs = $config['runAs'];
+        }
+        return (string) $runAs;
+    }
+
     private function getRootDir(array $config): string
     {
         $rootDir = getenv('BEHAT_ROOT_DIR');
diff --git a/tests/psalm-baseline.xml b/tests/psalm-baseline.xml
new file mode 100644
index 0000000..4e198d3
--- /dev/null
+++ b/tests/psalm-baseline.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="5.12.0@f90118cdeacd0088e7215e64c0c99ceca819e176">
+  <file src="src/Server.php">
+    <UndefinedInterfaceMethod>
+      <code>scalarNode</code>
+    </UndefinedInterfaceMethod>
+  </file>
+</files>