socket network not working

The socket network type is no longer working in 2.8.0.

When trying to establish a network between 2 qemu instances:

The listening host:
qemu-system-x86_64 -netdev socket,id=in0,listen=127.0.0.1:9999 -device virtio-net-pci,netdev=in0

works fine, but for the second one:

qemu-system-x86_64 -netdev socket,id=in0,connect=127.0.0.1:9999 -device virtio-net-pci,netdev=in0

It fails with:

qemu-system-x86_64: -device virtio-net-pci,netdev=in0: Property 'virtio-net-device.netdev' can't find value 'in0'

netstat shows a new connection to port 9999 in time_wait state every time.

host: kernel 4.4.38, 64bits.

It was working fine with previous version.