diff --git a/composer.json b/composer.json
index 9a9eefab..783271d1 100644
--- a/composer.json
+++ b/composer.json
@@ -16,14 +16,15 @@
     },
     "require-dev": {
         "wp-cli/entity-command": "^1.3 || ^2",
-        "wp-cli/wp-cli-tests": "^4"
+        "wp-cli/wp-cli-tests": "^5"
     },
     "config": {
         "process-timeout": 7200,
         "sort-packages": true,
         "allow-plugins": {
             "dealerdirect/phpcodesniffer-composer-installer": true,
-            "johnpbloch/wordpress-core-installer": true
+            "johnpbloch/wordpress-core-installer": true,
+            "phpstan/extension-installer": true
         },
         "lock": false
     },
@@ -54,12 +55,14 @@
         "behat-rerun": "rerun-behat-tests",
         "lint": "run-linter-tests",
         "phpcs": "run-phpcs-tests",
+        "phpstan": "run-phpstan-tests",
         "phpcbf": "run-phpcbf-cleanup",
         "phpunit": "run-php-unit-tests",
         "prepare-tests": "install-package-tests",
         "test": [
             "@lint",
             "@phpcs",
+            "@phpstan",
             "@phpunit",
             "@behat"
         ]
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 00000000..64d88315
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,13 @@
+parameters:
+  level: 9
+  paths:
+    - src
+    - super-admin-command.php
+  scanDirectories:
+    - vendor/wp-cli/wp-cli/php
+  scanFiles:
+    - vendor/php-stubs/wordpress-stubs/wordpress-stubs.php
+  treatPhpDocTypesAsCertain: false
+  ignoreErrors:
+    - identifier: missingType.parameter
+    - identifier: missingType.return
diff --git a/src/Super_Admin_Command.php b/src/Super_Admin_Command.php
index 55ecada5..b05dce35 100644
--- a/src/Super_Admin_Command.php
+++ b/src/Super_Admin_Command.php
@@ -24,10 +24,16 @@
  */
 class Super_Admin_Command extends WP_CLI_Command {
 
+	/**
+	 * @var array<string>
+	 */
 	private $fields = [
 		'user_login',
 	];
 
+	/**
+	 * @var \WP_CLI\Fetchers\User
+	 */
 	private $fetcher;
 
 	public function __construct() {
@@ -84,6 +90,9 @@ public function list_subcommand( $_, $assoc_args ) {
 
 				$user_ids = [];
 				foreach ( $super_admins as $user_login ) {
+					/**
+					 * @var \WP_User $user_obj
+					 */
 					$user_obj   = get_user_by( 'login', $user_login );
 					$user_ids[] = $user_obj->ID;
 				}