VBoxManage: Shrink VDI file... not implemeted yet!

[palmito]

Trying to shrink a VDI file but get the following error.
Already zerofree the partition, cloned it... but still same error

vboxmanage modifymedium "C:\Users\CarlosPalminha\VirtualBox VMs\Xubuntu\Xubuntu.vdi" --resize 17000
0%...
Progress state: VBOX_E_NOT_SUPPORTED
VBoxManage.exe: error: Resize medium operation for this format is not implemented yet!

[mpack]

Shrinking a VDI is not supported. In non-expert hands that could destroy the contents of the drive.

Did you intend to compact? Otherwise the mention of zerofree seems irrelevant.