exports in config not work

[exotfboy]

I am using the latest closure-util to build my application with ol ,however the following config works but does not export ol.Map.

{
  "lib": [
	"node_modules/openlayers/src/**/*.js",
	"node_modules/openlayers/build/ol.ext/**/*.js",
	"src/**/*.js"
  ],
  "exports": [
    "ol.Map"
  ],

When I say works I mean that my bundled application works as expected.

It seems that the exports does not take effect as expected.

So I want to know how closure-util deal with exports ?