Get-PowerBIDataset error message: Guid should contain 32 digits...

When I use Get-PowerBIDataset and pass the GUID of a personal workspace as parameter, it crashes with 

Get-PowerBIDataset : Guid should contain 32 digits with 4 dashes (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).

Even though the parameter is well-formed.  However, it works fine with the GUIDs of "regular" workspaces.  Has anybody experienced this?

Thanks,

Adolfo