diff --git a/appinfo/app.php b/appinfo/app.php
index 74f8aa8..57baa18 100644
--- a/appinfo/app.php
+++ b/appinfo/app.php
@@ -82,10 +82,7 @@ if($returnScript === true) {
 }
 
 $app = new \OCA\User_SAML\AppInfo\Application();
-$dispatcher = \OC::$server->getEventDispatcher();
-if ($type === 'environment-variable') {
-	$app->registerDavAuth();
-}
+$app->registerDavAuth();
 
 $redirectSituation = false;
 
diff --git a/lib/DavPlugin.php b/lib/DavPlugin.php
index 1545d71..c90c9a6 100644
--- a/lib/DavPlugin.php
+++ b/lib/DavPlugin.php
@@ -23,13 +23,20 @@ namespace OCA\User_SAML;
 
 use OCP\IConfig;
 use OCP\ISession;
+use Sabre\DAV\CorePlugin;
+use Sabre\DAV\FS\Directory;
 use Sabre\DAV\Server;
 use Sabre\DAV\ServerPlugin;
+use Sabre\DAV\Tree;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
 
 class DavPlugin extends ServerPlugin {
 	private $session;
 	private $config;
 	private $auth;
+	/** @var Server */
+	private $server;
 
 	public function __construct(ISession $session, IConfig $config, array $auth) {
 		$this->session = $session;
@@ -41,14 +48,28 @@ class DavPlugin extends ServerPlugin {
 	public function initialize(Server $server) {
 		// before auth
 		$server->on('beforeMethod', [$this, 'beforeMethod'], 9);
+		$this->server = $server;
 	}
 
-	public function beforeMethod() {
-		if (!$this->session->exists('user_saml.samlUserData')) {
+	public function beforeMethod(RequestInterface $request, ResponseInterface $response) {
+		if (
+			$this->config->getAppValue('user_saml', 'type') === 'environment-variable' &&
+			!$this->session->exists('user_saml.samlUserData')
+		) {
 			$uidMapping = $this->config->getAppValue('user_saml', 'general-uid_mapping');
 			if (isset($this->auth[$uidMapping])) {
 				$this->session->set('user_saml.samlUserData', $this->auth);
 			}
 		}
+
+		if ($request->getMethod() === 'OPTIONS' && $request->getPath() === '') {
+			/** @var CorePlugin $corePlugin */
+			$corePlugin = $this->server->getPlugin('core');
+			// setup a fake tree for anonymous access
+			$this->server->tree = new Tree(new Directory(''));
+			$corePlugin->httpOptions($request, $response);
+			$this->server->sapi->sendResponse($response);
+			return false;
+		}
 	}
 }