COMMUTATOR doesn't seem to work

Maybe I am using it wrong but I get no error message when I use it.  I
have a type called chkpass (a version is in the additional supplied
modules) and I create the equality operator like this:

CREATE OPERATOR = (        PROCEDURE = eq,        LEFTARG = chkpass,        RIGHTARG = text,        COMMUTATOR = =,        NEGATOR = <>
);

This works;

cosmostest=# SELECT 'aaa'::chkpass = 'aaa'; ?column?
---------- t
(1 row)

But...

cosmostest=# SELECT 'aaa' = 'aaa'::chkpass;
ERROR:  operator is only a shell: text = chkpass
LINE 1: SELECT 'aaa' = 'aaa'::chkpass;

When I look at the operators I see why, sort of...
 public | =    | chkpass       | text           | boolean     | public | =    | text          | chkpass        | -           |

So while it created the operator it didn't set a return type.

I don't know if this is a new issue or I simply got lucky and never
tried the opposite test before but I see this in 9.0.4 and 9.1.3.
Am I using the command improperly?

-- 
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