How to build Packer AMI using GP3?

Using Packer to build AWS AMIs. The default type is GP2. I’d like to build on GP3. I’ve tried:

"builders": [{
    "type": "amazon-ebs",
    "launch_block_device_mappings": [{
        "volume_type": "gp3",
        "volume_size": "3",
        "device_name": "/dev/nvme0n1p2"

But I keep getting an error that /dev/nvme0n1p2 is an invalid device name. /dev/nvme0n1p2 is the device root is being built on. I have also tried /dev/nvme0n1, /dev/nvme0, and even /dev/sda all with the same error.

What’s going on here?

I just read something that as of 1.7.x GP3 is supposed to be the default volume type. I’m running 1.8.4 and GP2 is still being used by default.