Got generic error Exception calling "MoveTo" with "1" argument(s): "Failure" during Move-SFTPItem

[Agent-E11]

$cred = New-Object System.Management.Automation.PSCredential ("<username>", (ConvertTo-SecureString -String '<password>' -AsPlainText -Force))
$session = New-SFTPSession -ComputerName host.domain.com -Credential $cred
Move-SFTPItem -SFTPSession $session -Path /outbox/testfile.txt -Destination /upload/archive

Exception calling "MoveTo" with "1" argument(s): "Failure"
At C:\Users\agent-e11\Documents\WindowsPowerShell\Modules\Posh-SSH\3.2.0\Posh-SSH.psm1:1393 char:17
+                 $itemInfo.MoveTo($Destination)
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : SshException

This is a very generic error, and there is no hint as to what is wrong. I finally tried including the destination filename along with the directory, and it worked, but I think the error message should be more useful.