* @param IMaintainableDatabase $db A database subclass
* @param array $tablesToClone An array of tables to clone, unprefixed
* @param string $newTablePrefix Prefix to assign to the tables
- * @param string $oldTablePrefix Prefix on current tables, if not $wgDBprefix
+ * @param string|null $oldTablePrefix Prefix on current tables, if not $wgDBprefix
* @param bool $dropCurrentTables
*/
public function __construct( IMaintainableDatabase $db, array $tablesToClone,