SortedMap reversed() fails with exception

[wittlesouth]

The following code:

const sm = new SortedMap()
// Fill SortedMap
const sm_desc = sm.reversed()

fails with "TypeError: this.constructClone(...).reverse is not a function", specifically on line 267 of generic-collection.js.GenericCollection.reversed. Per the docs, I was expecting it to return a copy with the items in reversed order of keys.