Why does accessing a parameter variable's attributes with Get-Variable only work the first time in the ISE?

Thanks to the great people at StackOverflow we received a very good answer on how to retrieve the values defined in ValidateSet within the Param() clause of a script or function:

Param (
    [ValidateSet('Startup', 'Shutdown', 'LogOn', 'LogOff')]
    [String]$Type = 'Startup'
)

(Get-Variable Type).Attributes.ValidValues

The only thing that bothers me is that this code only works the first time when you run it in the PowerShell ISE. The second time you run it, there is no output generated.

Is there a workaround to have it always working? We use PowerShell 4.0 on Win 7 and Win 2012.