diff --git a/lib/Helper/Trace.php b/lib/Helper/Trace.php
new file mode 100644
index 000000000..c8cfbea0e
--- /dev/null
+++ b/lib/Helper/Trace.php
@@ -0,0 +1,54 @@
+<?php
+/**
+ * @copyright Copyright (c) 2021 René Gieling <github@dartcafe.de>
+ *
+ * @author René Gieling <github@dartcafe.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as
+ *  published by the Free Software Foundation, either version 3 of the
+ *  License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Polls\Model;
+
+class Trace implements \JsonSerializable {
+
+	/** @var Array */
+	protected $result = [];
+
+	/** @var string */
+	protected $method;
+
+	public function __construct(
+		string $method,
+		string $payload = ''
+	) {
+		$this->method = $method;
+		$this->log('Initialization', $payload);
+	}
+
+	public function log($operation, $payload = '') {
+		$this->result[] = [
+			'method' => $this->method,
+			'time' => time(),
+			'operation' => $operation,
+			'payload' => $payload
+		];
+	}
+
+	public function jsonSerialize(): array {
+		return $this->result;
+	}
+}
diff --git a/lib/Service/SystemService.php b/lib/Service/SystemService.php
index cd5657da0..41c705421 100644
--- a/lib/Service/SystemService.php
+++ b/lib/Service/SystemService.php
@@ -141,7 +141,7 @@ class SystemService {
 		}
 
 		// get all users
-		foreach (User::search() as $user) {
+		foreach (User::search($userName) as $user) {
 			if ($userName === strtolower(trim($user->getId()))
 				|| $userName === strtolower(trim($user->getDisplayName()))) {
 				throw new InvalidUsernameException;