diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index a6c00a59174ce..1424ee4f9be2a 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -2347,7 +2347,7 @@ public function getCalendarObjectById(string $principalUri, int $id): ?array {
 	 * @param int $syncLevel
 	 * @param int|null $limit
 	 * @param int $calendarType
-	 * @return array
+	 * @return ?array
 	 */
 	public function getChangesForCalendar($calendarId, $syncToken, $syncLevel, $limit = null, $calendarType = self::CALENDAR_TYPE_CALENDAR) {
 		$table = $calendarType === self::CALENDAR_TYPE_CALENDAR ? 'calendars': 'calendarsubscriptions';
diff --git a/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php b/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
index db5da97f27588..39697a7cb7ede 100644
--- a/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
+++ b/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
@@ -112,8 +112,8 @@ public function deleteByUser(string $uid): array {
 
 		return array_map(function (array $row) {
 			return [
-				'provider_id' => $row['provider_id'],
-				'uid' => $row['uid'],
+				'provider_id' => (string) $row['provider_id'],
+				'uid' => (string) $row['uid'],
 				'enabled' => (int) $row['enabled'] === 1,
 			];
 		}, $rows);
diff --git a/lib/public/DB/IResult.php b/lib/public/DB/IResult.php
index 10a60cd5ff4e1..154dcdf9029ad 100644
--- a/lib/public/DB/IResult.php
+++ b/lib/public/DB/IResult.php
@@ -63,7 +63,7 @@ public function fetch(int $fetchMode = PDO::FETCH_ASSOC);
 	/**
 	 * @param int $fetchMode (one of PDO::FETCH_ASSOC, PDO::FETCH_NUM or PDO::FETCH_COLUMN (2, 3 or 7)
 	 *
-	 * @return mixed[]
+	 * @return list<mixed>
 	 *
 	 * @since 21.0.0
 	 */