J4 Alpha 6 update fails

[Webdongle]

Steps to reproduce the issue

Install Joomla 3.9.1
Update by custom url https://update.joomla.org/core/nightlies/next_major_list.xml or by downloading the update package and using Joomla upload and install

Expected result

Update should work

Actual result

ERROR:
Invalid AJAX data:

( ! ) Fatal error: Uncaught Error: Class 'Joomla\CMS\Filesystem\AKFactory' not found in C:\wamp64-3-1-4\www\j391\administrator\components\com_joomlaupdate\restore_finalisation.php on line 124
( ! ) Error: Class 'Joomla\CMS\Filesystem\AKFactory' not found in C:\wamp64-3-1-4\www\j391\administrator\components\com_joomlaupdate\restore_finalisation.php on line 124
Call Stack
#	Time	Memory	Function	Location
1	0.0007	463536	{main}( )	...\restore.php:0
2	0.0373	535184	finalizeRestore( )	...\restore.php:8335
3	0.0650	536952	JoomlaInstallerScript->deleteUnexistingFiles( )	...\restore_finalisation.php:75
4	0.0662	537048	Joomla\CMS\Filesystem\File::delete( )	...\script.php:3952

System information (as much as possible)

Additional comments

[Quy]

Duplicate #23315 ?

[richard67]

Expected result is wrong. There is no valid update path from 3.9 to 4.0. See discussion in #23315 .

[joomla-cms-bot]

Set to "closed" on behalf of @Quy by The JTracker Application at issues.joomla.org/joomla-cms/23346