What is the working syntax to specify the binding:profile port attribute with the neutron command line?

These attempts don't work (Icehouse release):

$ neutron port-create --name P4 4 --binding:profile foo=1
Invalid input for binding:profile. Reason: 'foo=1' is not a dictionary.
$ neutron port-create --name P4 4 --binding:profile '{"foo":1}'
Invalid input for binding:profile. Reason: '{"foo":1}' is not a dictionary.