diff --git a/lam/templates/login.php b/lam/templates/login.php
index 842c16fa8..211c06b43 100644
--- a/lam/templates/login.php
+++ b/lam/templates/login.php
@@ -1,5 +1,6 @@
 <?php
 namespace LAM\LOGIN;
+use LAM\ENV\LAMLicenseValidator;
 use LAM\LIB\TWO_FACTOR\TwoFactorProviderService;
 use \LAMConfig;
 use \LAMCfgMain;
@@ -189,13 +190,13 @@ setlanguage(); // setting correct language
 /**
  * Displays the login window.
  *
- * @param \LAM\ENV\LAMLicenseValidator $licenseValidator license validator
- * @param string $error_message error message to display
- * @param string $errorDetails error details
- * @param string $extraMessage extra message that is shown as info
+ * @param LAMLicenseValidator|null $licenseValidator license validator
+ * @param string|null $error_message error message to display
+ * @param string|null $errorDetails error details
+ * @param string|null $extraMessage extra message that is shown as info
  * @throws LAMException error rendering login page
  */
-function display_LoginPage($licenseValidator, $error_message, $errorDetails = null, $extraMessage = null): void {
+function display_LoginPage(?LAMLicenseValidator $licenseValidator, ?string $error_message, ?string $errorDetails = null, ?string $extraMessage = null): void {
 	$config_object = $_SESSION['config'];
 	$cfgMain = $_SESSION["cfgMain"];
 	logNewMessage(LOG_DEBUG, "Display login page");
diff --git a/lam/templates/misc/ajax.php b/lam/templates/misc/ajax.php
index 0a5c7efca..02d71bd16 100644
--- a/lam/templates/misc/ajax.php
+++ b/lam/templates/misc/ajax.php
@@ -409,7 +409,7 @@ class Ajax {
 		$dn = trim($_POST['dn']);
 		if (empty($dn) || !get_preg($dn, 'dn')) {
 			$dnList = $this->getDefaultDns();
-			$dn = null;
+			return '';
 		}
 		else {
 			$dnList = $this->getSubDns($dn);
diff --git a/lam/templates/upload/massBuildAccounts.php b/lam/templates/upload/massBuildAccounts.php
index 06efc8668..1a0cffd3e 100644
--- a/lam/templates/upload/massBuildAccounts.php
+++ b/lam/templates/upload/massBuildAccounts.php
@@ -74,6 +74,9 @@ if (isset($_POST['showldif'])) {
 	header('Content-Type: text/plain');
 	header('Content-disposition: attachment; filename=lam.ldif');
 	$accounts = unserialize(lamDecrypt($_SESSION['mass_accounts']));
+	if ($accounts === false) {
+		exit;
+	}
 	foreach ($accounts as $account) {
 		echo "DN: " . $account['dn'] . "\n";
 		unset($account['dn']);
diff --git a/phpstan.neon b/phpstan.neon
index 930bad0d3..0f0174d9e 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,5 @@
 parameters:
-	level: 8
+	level: 9
 	scanDirectories:
 		- lam/lib
 		- lam/templates
@@ -38,3 +38,13 @@ parameters:
 		- '#Parameter \#1 \$ldap of function ldap_get_entries expects LDAP\\Connection, resource given.#'
 		- '#Parameter \#1 \$string of function htmlspecialchars expects string, array\|string given.#'
 		- '#Parameter \#1 \$name of function LAM\\ACCOUNTLIST\\search_username expects string, array\|string given.#'
+		- '#Cannot access offset int\|string on mixed.#'
+		- '#Parameter \#1 \$array of function array_keys expects array, mixed given.#'
+		- '#Cannot access offset .+ on mixed.#'
+		- '#Argument of an invalid type mixed supplied for foreach, only iterables are supported.#'
+		- '#Parameter \#1 \$string of function htmlspecialchars expects string, mixed given.#'
+		- '#Parameter \#2 \$args of function call_user_func_array expects array<int\|string, mixed>, mixed given.#'
+		- '#Parameter \#2 \$user of function LAM\\ACCOUNTLIST\\setSpecifiedPassword expects array, array\|null given.#'
+		- '#Parameter \#2 \$user of function LAM\\ACCOUNTLIST\\generatePassword expects array, array\|null given.#'
+		- '#Parameter \#2 \$attributes of function LAM\\ACCOUNTLIST\\unlock expects array, array\|null given.#'
+		- '#Parameter \#2 \$attributes of function LAM\\ACCOUNTLIST\\lock expects array, array\|null given.#'