MAAS fails to add a DHCP snippet with "subnet6 statement is only supported in DHCPv6 mode."

On a fresh install of MAAS on 16.04 MAAS cannot add ANY snippet, even a comment. It always fails with:

 {"value": ["subnet6 statement is only supported in DHCPv6 mode."]}

I have tried from the UI and the command line.

Here's the exception:

2016-05-25 15:02:31 [-] Error on request (17) dhcpsnippet.create: {"value": ["subnet6 statement is only supported in DHCPv6 mode."]}
 Traceback (most recent call last):
   File "/usr/lib/python3.5/threading.py", line 862, in run
     self._target(*self._args, **self._kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 841, in worker
     return target()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_threadworker.py", line 46, in work
     task()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_team.py", line 190, in doWork
     task()
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 246, in inContext
     result = inContext.theWork()
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 262, in <lambda>
     inContext.theWork = lambda: context.call(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 118, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 874, in callInContext
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 516, in call_within_transaction
     return func_outside_txn(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 343, in retrier
     return func(*args, **kwargs)
   File "/usr/lib/python3.5/contextlib.py", line 30, in inner
     return func(*args, **kwds)
   File "/usr/lib/python3/dist-packages/maasserver/websockets/handlers/dhcpsnippet.py", line 66, in create
     return super().create(params)
   File "/usr/lib/python3/dist-packages/maasserver/websockets/base.py", line 375, in create
     raise HandlerValidationError(form.errors)
 maasserver.websockets.base.HandlerValidationError: {'value': ['subnet6 statement is only supported in DHCPv6 mode.']}

MAAS Packages:

student@torc0:/var/log$ dpkg -l '*maas*' | cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-===============================-============================-============-=================================================
ii maas 2.0.0~beta3+bzr4941-0ubuntu1 all "Metal as a Service" is a physical cloud and IPAM
ii maas-cli 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS client and command-line interface
un maas-cluster-controller <none> <none> (no description available)
ii maas-common 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS server common files
ii maas-dhcp 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS DHCP server
ii maas-dns 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS DNS server
ii maas-proxy 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS Caching Proxy
ii maas-rack-controller 2.0.0~beta3+bzr4941-0ubuntu1 all Rack Controller for MAAS
ii maas-region-api 2.0.0~beta3+bzr4941-0ubuntu1 all Region controller API service for MAAS
ii maas-region-controller 2.0.0~beta3+bzr4941-0ubuntu1 all Region Controller for MAAS
un maas-region-controller-min <none> <none> (no description available)
un python-django-maas <none> <none> (no description available)
un python-maas-client <none> <none> (no description available)
un python-maas-provisioningserver <none> <none> (no description available)
ii python3-django-maas 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS server Django web framework (Python 3)
ii python3-maas-client 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS python API client (Python 3)
ii python3-maas-provisioningserver 2.0.0~beta3+bzr4941-0ubuntu1 all MAAS server provisioning libraries (Python 3)

Logs attached.