jQuery: How can I create a catch-all Ajax transport?

ajax-transport.js

// When I set up a json-specific transport...
$.ajaxTransport("json", function(options) {
  console.log("json", options);
});

// The json options are logged.
$.getJSON("/foo");


// When I try to set up a catch-all transport...
$.ajaxTransport("*", function(options) {
  console.log("catch-all", options);
});

// Nothing is logged. The transport factory function doesn't execute.
$.ajax("/foo");

Thanks! I must have missed the + in the docs.