set-vm(guest customisation) : The operation for the entity "x" failed with the following message: "A specified parameter was not correct: hostname

Question

(powercli newbie here)

I am using guest customisationscript that needs hostname when creating vm. Using that in powercli fails

$New_vm=get-vm "ies-jtmpl-t005"
$OSSpecs = Get-OSCustomizationSpec -Name 'jayan_debug'
Set-VM -VM $New_vm -OSCustomizationSpec $OSSpecs -Confirm:$false

The jayan_debug is set to take hostname when creating vm

The operation for the entity "ies-jtmpl-t005" failed with the following message: "A 
specified parameter was not correct: hostname"

How do I pass hostname