Get-VMHostPatch returns nothing for ESXi 5.1 hosts

In my environment the Get-VMHostPatch cmdlet does not return anything for ESXi 5.1 hosts. For ESXi 4.1 the cmdlet runs as expected. I am sure that the ESXi 5.1 hosts have some patches installed. This looks like a bug to me. Does anyone else see this behaviour?

I tested this with PowerShell v2 and PowerCLI 5.1 Release 1 build 793510.