diff --git a/lib/FilesHooks.php b/lib/FilesHooks.php
index 296f90bd3..440bf3879 100755
--- a/lib/FilesHooks.php
+++ b/lib/FilesHooks.php
@@ -151,7 +151,7 @@ protected function addNotificationsForFileAction($filePath, $activityType, $subj
 			$this->generateRemoteActivity($accessList['remotes'], $activityType, time(), $this->currentUser->getCloudId(), $accessList['ownerPath']);
 		}
 
-		$affectedUsers = $accessList['users'];
+		$affectedUsers = $accessList['users'] ?? [];
 
 		// file can be shared using GroupFolders, including ACL check
 		if ($this->config->getSystemValueBool('activity_use_cached_mountpoints', false)) {