diff --git a/lib/private/Collaboration/Collaborators/MailPlugin.php b/lib/private/Collaboration/Collaborators/MailPlugin.php
index 55e3945ace2f0..730be14a1d170 100644
--- a/lib/private/Collaboration/Collaborators/MailPlugin.php
+++ b/lib/private/Collaboration/Collaborators/MailPlugin.php
@@ -159,6 +159,9 @@ public function search($search, $limit, $offset, ISearchResult $searchResult): b
 
 						if ($this->shareeEnumeration) {
 							try {
+								if (!isset($contact['CLOUD'])) {
+									continue;
+								}
 								$cloud = $this->cloudIdManager->resolveCloudId($contact['CLOUD'][0] ?? '');
 							} catch (\InvalidArgumentException $e) {
 								continue;