Unable to call an overloaded UDF

Hello,

I have created 2 functions with the same name, and I am unable to call one of them. The first one does not have any parameters, and the second one has a single parameter with a default value. The error message I get makes sense to me, however the hint is not so helpful as I do not see any way I can do a type cast that will make Postgres call the function without any parameters in the definition.

Is there a way to make this work? Can this be a bug that needs fixing, or is it a known and intended feature?

Function definitions:

CREATE FUNCTION f() RETURNS int as $$ SELECT 1 $$ LANGUAGE SQL;
CREATE FUNCTION f(param int DEFAULT 1) RETURNS int as $$ SELECT param $$ LANGUAGE SQL;

Error message after I ran a simple query:

postgres # SELECT f();
ERROR: 42725: function f() is not unique
LINE 1: SELECT f();
^
HINT: Could not choose a best candidate function. You might need to add explicit type casts.
LOCATION: ParseFuncOrColumn, parse_func.c:577

Best,
Hanefi