diff --git a/lib/Chat/AutoComplete/SearchPlugin.php b/lib/Chat/AutoComplete/SearchPlugin.php
index 2d077880a5fc..68e8d27d2c92 100644
--- a/lib/Chat/AutoComplete/SearchPlugin.php
+++ b/lib/Chat/AutoComplete/SearchPlugin.php
@@ -71,7 +71,11 @@ public function search($search, $limit, $offset, ISearchResult $searchResult): b
 		if ($this->room->getObjectType() === 'file') {
 			$usersWithFileAccess = $this->util->getUsersWithAccessFile($this->room->getObjectId());
 			if (!empty($usersWithFileAccess)) {
-				$this->searchUsers($search, $usersWithFileAccess, $searchResult);
+				$users = [];
+				foreach ($usersWithFileAccess as $userId) {
+					$users[$userId] = $this->userManager->getDisplayName($userId) ?? $userId;
+				}
+				$this->searchUsers($search, $users, $searchResult);
 			}
 		}
 
diff --git a/lib/Files/Util.php b/lib/Files/Util.php
index 9c5f73697aa9..6755d298db27 100644
--- a/lib/Files/Util.php
+++ b/lib/Files/Util.php
@@ -48,6 +48,9 @@ public function __construct(
 	) {
 	}
 
+	/**
+	 * @return string[]
+	 */
 	public function getUsersWithAccessFile(string $fileId): array {
 		if (!isset($this->accessLists[$fileId])) {
 			$nodes = $this->rootFolder->getById((int) $fileId);