diff --git a/setup/backup.class.inc.php b/setup/backup.class.inc.php
index 6e2cddd75..f7f8fd9c0 100644
--- a/setup/backup.class.inc.php
+++ b/setup/backup.class.inc.php
@@ -147,12 +147,12 @@ class DBBackup
 	 * Create a normalized backup name, depending on the current date/time and Database
 	 *
 	 * @param string $sNameSpec Name and path, eventually containing itop placeholders + time formatting following the strftime() format {@link https://www.php.net/manual/fr/function.strftime.php}
-	 * @param \DateTime|null $oDateTime Date time to use for the name
+	 * @param ?\DateTime|null $oDateTime Date time to use for the name
 	 *
 	 * @return ?string Name of the backup file WITHOUT the file extension (eg. `.tar.gz`)
 	 * @since 3.1.0 N°5279 Add $oDateTime parameter
 	 */
-	public function MakeName(?string $sNameSpec = "__DB__-%Y-%m-%d", DateTime $oDateTime = null)
+	public function MakeName(?string $sNameSpec = "__DB__-%Y-%m-%d", ?DateTime $oDateTime = null)
 	{
 		if ($oDateTime === null) {
 			$oDateTime = new DateTime();