Set-VMHostAuthentication error

$ESXHOST = Read-Host "Enter ESX Host Name or IP"

Connect-VIServer $ESXHOST

$domain = "MyDomain"

Write-Host "Join to domain $domain"

$cred = Get-Credential # Prompt for the user and password

#Write-Host "Credentials: $cred"

$host | Get-VMHostAuthentication | Set-VMHostAuthentication -Domain $domain -Credential $cred

exit

PowerCLI E:\PowerCLI 5.0\Scripts> .\Join.ps1

Enter ESX Host Name or IP: esx22

Name Port User

---- ---- ----

esx122 443 root

Join to domain SCS.local

cmdlet Get-Credential at command pipeline position 1

Supply values for the following parameters:

Credential

cmdlet Set-VMHostAuthentication at command pipeline position 2

Supply values for the following parameters:

JoinDomain: scs.local

Set-VMHostAuthentication : Cannot convert 'System.String' to the type 'System.Management.Automation.SwitchParameter' required by

parameter 'JoinDomain'.

At E:\PowerCLI 5.0\Scripts\RSA\RSA_Join.ps1:10 char:60

+ $host | Get-VMHostAuthentication | Set-VMHostAuthentication <<<< -Domain scs.local -Credential $cred

+ CategoryInfo : InvalidArgument: (:) [Set-VMHostAuthentication], ParameterBindingException

+ FullyQualifiedErrorId : CannotConvertArgument,VMware.VimAutomation.ViCore.Cmdlets.Commands.Host.SetVMHostAuthentication

Even though I have specified the domain "MyDomain" I get prompted "Join to domain:", and even though I get the error which probably is about the Set-VMHostAuthentication.

Shouldn't it be straight forward ?