zul with hashmap not load key from a fx

Example: http://zkfiddle.org/sample/1j62rqa/4-zul-with-hashmap-not-load-key-from-a-fx

Binder can't load value from a fx when:

<!-- WORK -->
<label value="@load(fx.hash[vm.key])"></label>

<!-- WORK TO -->
<label value="@load(vm.hash[vm.key])"></label>

<!-- NOT WORK -->
<label value="@load(fx.hash[fx.key])"></label>