diff --git a/apps/user_ldap/lib/Migration/Version1190Date20230706134108.php b/apps/user_ldap/lib/Migration/Version1190Date20230706134108.php
index 4e3e44a5f21da..e0740514d75f2 100644
--- a/apps/user_ldap/lib/Migration/Version1190Date20230706134108.php
+++ b/apps/user_ldap/lib/Migration/Version1190Date20230706134108.php
@@ -99,6 +99,10 @@ protected function copyGroupMembershipData(): void {
 		$result = $query->executeQuery();
 		while ($row = $result->fetch()) {
 			$knownUsers = unserialize($row['owncloudusers']);
+			if (!is_array($knownUsers)) {
+				/* Unserialize failed or data was incorrect in database, ignore */
+				continue;
+			}
 			$knownUsers = array_unique($knownUsers);
 			foreach ($knownUsers as $knownUser) {
 				try {