How to clear a logging action buffer?

RouterOS Scripting
1

Given a logging action buffer in memory, how do I clear it?

For instance this logging action buffer failedauth:

/system logging action add memory-lines=1000 memory-stop-on-full=no name=failedauth target=memory
/system logging add action=failedauth disabled=no prefix="" topics=critical,system,error

Somehow this trick does not work in RouterOS 6.37.1 to clear the logging action buffer:

{
  :local logBuffer "failedauth";
  :local lines;
  /system logging action {
     :set lines [get ($logBuffer) memory-lines];
     set ($logBuffer) memory-lines 1;
     set ($logBuffer) memory-lines $lines;
  };
  :put "$lines"
}

The trick is originally by http://www.vulninfo.com/index.php/block-ssh-brute-force-on-mikrotik-routeros/ and likely worked in the past.
–jeroen