diff --git a/apps/user_ldap/lib/Access.php b/apps/user_ldap/lib/Access.php
index 06ccbd23ac63d..c16e9bf9f15dc 100644
--- a/apps/user_ldap/lib/Access.php
+++ b/apps/user_ldap/lib/Access.php
@@ -155,12 +155,14 @@ public function getConnection() {
 
 	/**
 	 * reads a given attribute for an LDAP record identified by a DN
+	 *
 	 * @param string $dn the record in question
 	 * @param string $attr the attribute that shall be retrieved
 	 *        if empty, just check the record's existence
 	 * @param string $filter
 	 * @return array|false an array of values on success or an empty
 	 *          array if $attr is empty, false otherwise
+	 * @throws ServerNotAvailableException
 	 */
 	public function readAttribute($dn, $attr, $filter = 'objectClass=*') {
 		if(!$this->checkConnection()) {
@@ -242,6 +244,7 @@ public function readAttribute($dn, $attr, $filter = 'objectClass=*') {
 	 * @return array|bool false if there was any error, true if an exists check
 	 *                    was performed and the requested DN found, array with the
 	 *                    returned data on a successful usual operation
+	 * @throws ServerNotAvailableException
 	 */
 	public function executeRead($cr, $dn, $attribute, $filter, $maxResults) {
 		$this->initPagedSearch($filter, array($dn), array($attribute), $maxResults, 0);
diff --git a/apps/user_ldap/lib/User_LDAP.php b/apps/user_ldap/lib/User_LDAP.php
index dcfc5cc13b929..356c24ec3bf35 100644
--- a/apps/user_ldap/lib/User_LDAP.php
+++ b/apps/user_ldap/lib/User_LDAP.php
@@ -35,6 +35,7 @@
 
 namespace OCA\User_LDAP;
 
+use OC\ServerNotAvailableException;
 use OC\User\Backend;
 use OC\User\NoUserException;
 use OCA\User_LDAP\Exceptions\NotOnLDAP;
@@ -302,16 +303,18 @@ public function userExistsOnLDAP($user) {
 
 			try {
 				$uuid = $this->access->getUserMapper()->getUUIDByDN($dn);
-				if(!$uuid) {
+				if (!$uuid) {
 					return false;
 				}
 				$newDn = $this->access->getUserDnByUuid($uuid);
 				//check if renamed user is still valid by reapplying the ldap filter
-				if(!is_array($this->access->readAttribute($newDn, '', $this->access->connection->ldapUserFilter))) {
+				if (!is_array($this->access->readAttribute($newDn, '', $this->access->connection->ldapUserFilter))) {
 					return false;
 				}
 				$this->access->getUserMapper()->setDNbyUUID($newDn, $uuid);
 				return true;
+			} catch (ServerNotAvailableException $e) {
+				throw $e;
 			} catch (\Exception $e) {
 				return false;
 			}