unable to update enable_snat using router-update command

Currently enable_snat is allowed only when setting a gateway.

$ neutron router-gateway-set <router-name> <ext-network> --disable-net
$ neutron router-gateway-set <router-name> <ext-network> --enable-net

There should be provision to set this flag with update command too.
Like
$ neutron router-update --enable-snat
$ neutron router-update --disable-snat

On Neutron, with the below command:
curl -g -i -X PUT http://10.0.4.130:9696/v2.0/routers/deecfcf8-6a4d-494d-938e-515f5c9d5885.json -H "User-Agent: python-neutronclient" -H "Content-Type: application/json" -H "Accept: application/json" -H "X-Auth-Token: b964f5aed06147efa06d27392db4f4f4" -d '{"router": {"external_gateway_info": {"enable_snat": false}}}'

Actual Response:
HTTP/1.1 400 Bad Request
Content-Length: 234
Content-Type: application/json; charset=UTF-8
X-Openstack-Request-Id: req-ac54539c-74eb-4fc1-8eac-339c928c69a6
Date: Wed, 07 Sep 2016 08:31:22 GMT

{"NeutronError": {"message": "Invalid input for external_gateway_info. Reason: Validation of dictionary's keys failed. Expected keys: set(['network_id']) Provided keys: set([u'enable_snat'])."

Expected Response : That the external_gateway_info would have the SNAT disabled, even without the gateway network ID

In Other words,
Expectation is that user can be allowed to enable/disable SNAT independently if the External Gateway Network ID is set. If not,
then it should be avoided