Powershell changes are not affected in Web UI

Not the first time I noticed that sometimes PowerShell changes are not seen in UI. By example this script:

# change web description example
Start-SPAssignment -Global
$myWeb = Get-SPWeb http://myserver/myweb
$myWeb.Description = "Some test description"
$myWeb.Update()
Stop-SPAssignment -Global

seems to be ok, it works, and when I check it in powershell

$myWeb = Get-SPWeb http://myserver/myweb
$myWeb.Description

it shows new description. But in web interface

http://myserver/myweb/_layouts/15/prjsetng.aspx

I still do not see it

What I need to do to make it right

Using Win 2012 R2, SP2013, Powershell ISE.