Can't resize Home Assistant .vmdk

I plan to run Home Assistant as a virtual machine and created the VM in VirtualBox using the official .ova file on home-assistant.io/hassio/installation. Prior to starting the VM I wanted to expand the size from the default 6GB to 30GB via Virtual Media Manager but get the following error message

I’m running VirtualBox 5.2. Do I have to upgrade to the latest release of VirtualBox?