diff --git a/apps/files_encryption/tests/webdav.php b/apps/files_encryption/tests/webdav.php
index 83f4c0a77d..bdbc9d7ef0 100755
--- a/apps/files_encryption/tests/webdav.php
+++ b/apps/files_encryption/tests/webdav.php
@@ -206,12 +206,17 @@ class Webdav extends TestCase {
 	 * handle webdav request
 	 *
 	 * @param bool $body
-	 *
 	 * @note this init procedure is copied from /apps/files/appinfo/remote.php
 	 */
 	function handleWebdavRequest($body = false) {
 		// Backends
-		$authBackend = new \OC_Connector_Sabre_Auth();
+		$authBackend = $this->getMockBuilder('OC_Connector_Sabre_Auth')
+			->setMethods(['validateUserPass'])
+			->getMock();
+		$authBackend->expects($this->any())
+			->method('validateUserPass')
+			->will($this->returnValue(true));
+
 		$lockBackend = new \OC_Connector_Sabre_Locks();
 		$requestBackend = new \OC_Connector_Sabre_Request();
 
@@ -236,6 +241,10 @@ class Webdav extends TestCase {
 		$server->addPlugin(new \OC_Connector_Sabre_MaintenancePlugin());
 		$server->debugExceptions = true;
 
+		// Totally ugly hack to setup the FS
+		\OC::$server->getUserSession()->login($this->userId, $this->userId);
+		\OC_Util::setupFS($this->userId);
+
 		// And off we go!
 		if ($body) {
 			$server->httpRequest->setBody($body);
diff --git a/lib/private/connector/sabre/auth.php b/lib/private/connector/sabre/auth.php
index 6e1baca933..f40706b73e 100644
--- a/lib/private/connector/sabre/auth.php
+++ b/lib/private/connector/sabre/auth.php
@@ -22,25 +22,50 @@
  */
 
 class OC_Connector_Sabre_Auth extends \Sabre\DAV\Auth\Backend\AbstractBasic {
+	const DAV_AUTHENTICATED = 'AUTHENTICATED_TO_DAV_BACKEND';
+
+	/**
+	 * Whether the user has initially authenticated via DAV
+	 *
+	 * This is required for WebDAV clients that resent the cookies even when the
+	 * account was changed.
+	 *
+	 * @see https://github.com/owncloud/core/issues/13245
+	 *
+	 * @param string $username
+	 * @return bool
+	 */
+	protected function isDavAuthenticated($username) {
+		return !is_null(\OC::$server->getSession()->get(self::DAV_AUTHENTICATED)) &&
+		\OC::$server->getSession()->get(self::DAV_AUTHENTICATED) === $username;
+	}
+
 	/**
 	 * Validates a username and password
 	 *
 	 * This method should return true or false depending on if login
 	 * succeeded.
 	 *
+	 * @param string $username
+	 * @param string $password
 	 * @return bool
 	 */
 	protected function validateUserPass($username, $password) {
-		if (OC_User::isLoggedIn()) {
+		if (OC_User::isLoggedIn() &&
+			$this->isDavAuthenticated($username)
+		) {
 			OC_Util::setupFS(OC_User::getUser());
+			\OC::$server->getSession()->close();
 			return true;
 		} else {
-			OC_Util::setUpFS();//login hooks may need early access to the filesystem
+			OC_Util::setUpFS(); //login hooks may need early access to the filesystem
 			if(OC_User::login($username, $password)) {
 				OC_Util::setUpFS(OC_User::getUser());
+				\OC::$server->getSession()->set(self::DAV_AUTHENTICATED, $username);
+				\OC::$server->getSession()->close();
 				return true;
-			}
-			else{
+			} else {
+				\OC::$server->getSession()->close();
 				return false;
 			}
 		}
@@ -55,10 +80,10 @@ class OC_Connector_Sabre_Auth extends \Sabre\DAV\Auth\Backend\AbstractBasic {
 	 */
 	public function getCurrentUser() {
 		$user = OC_User::getUser();
-		if(!$user) {
-			return null;
+		if($user && $this->isDavAuthenticated($user)) {
+			return $user;
 		}
-		return $user;
+		return null;
 	}
 
 	/**
@@ -77,9 +102,6 @@ class OC_Connector_Sabre_Auth extends \Sabre\DAV\Auth\Backend\AbstractBasic {
 
 		$result = $this->auth($server, $realm);
 
-		// close the session - right after authentication there is not need to write to the session any more
-		\OC::$server->getSession()->close();
-
 		return $result;
     }
 
@@ -89,7 +111,7 @@ class OC_Connector_Sabre_Auth extends \Sabre\DAV\Auth\Backend\AbstractBasic {
 	 * @return bool
 	 */
 	private function auth(\Sabre\DAV\Server $server, $realm) {
-		if (OC_User::handleApacheAuth() || OC_User::isLoggedIn()) {
+		if (OC_User::handleApacheAuth()) {
 			$user = OC_User::getUser();
 			OC_Util::setupFS($user);
 			$this->currentUser = $user;