diff --git a/lib/private/User/Manager.php b/lib/private/User/Manager.php
index f41468d492..7d8c6d48b2 100644
--- a/lib/private/User/Manager.php
+++ b/lib/private/User/Manager.php
@@ -157,6 +157,16 @@ class Manager extends PublicEmitter implements IUserManager {
 			return $this->cachedUsers[$uid];
 		}
 
+		if (method_exists($backend, 'loginName2UserName')) {
+			$loginName = $backend->loginName2UserName($uid);
+			if ($loginName !== false) {
+				$uid = $loginName;
+			}
+			if (isset($this->cachedUsers[$uid])) {
+				return $this->cachedUsers[$uid];
+			}
+		}
+
 		$user = new User($uid, $backend, $this, $this->config);
 		if ($cacheUser) {
 			$this->cachedUsers[$uid] = $user;