QEMU arm doesn't work

When running ./pmbootstrap.py qemu --arch=arm (on a x86_64 host) I get the following error in the log.

(019941) [20:07:11] WARNING: Qemu is not using KVM and will run slower!
(019941) [20:07:11] % sudo chmod 666 /home/luca/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-vexpress.img
(019941) [20:07:11] NOTE: Run 'pmbootstrap qemu --image-size 2G' to set the system image size when you run out of space!
(019941) [20:07:11] Connect to the VM (telnet requires 'pmbootstrap initfs hook_add usb-shell'):
(019941) [20:07:11] * (ssh) ssh -p 2222 user@localhost
(019941) [20:07:11] * (telnet) telnet localhost 2224
(019941) [20:07:11] % qemu-system-arm -kernel /home/luca/.local/var/pmbootstrap/chroot_rootfs_qemu-vexpress/boot/vmlinuz-postmarketos-stable -initrd /home/luca/.local/var/pmbootstrap/chroot
_rootfs_qemu-vexpress/boot/initramfs-postmarketos-stable -append "console=ttyAMA0,38400n8 console=tty1 PMOS_NO_OUTPUT_REDIRECT PMOS_FORCE_PARTITION_RESIZE" -m 1024 -netdev user,id=net0,host
fwd=tcp::2222-:22,hostfwd=tcp::2224-:24,net=172.16.42.0/24,dhcpstart=172.16.42.1 -show-cursor -dtb /home/luca/.local/var/pmbootstrap/chroot_rootfs_qemu-vexpress/usr/share/dtb/vexpress-v2p-c
a9.dtb -M vexpress-a9 -sd /home/luca/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-vexpress.img -device virtio-net-device,netdev=net0 -vga virtio -display sdl,gl=on
WARNING: Image format was not specified for '/home/luca/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-vexpress.img' and probing guessed raw.
         Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.
qemu-system-arm: Virtio VGA not available

The same error happens when running ./pmbootstrap qemu on an ARM board.