Validation not working with mapping plugin. (With jsFiddle example)

For some reason I cannot understand, the validation plugin does not want to work with properties of an observable populated via the knockout mapping plugin. Although the individual properties correctly raise an error if blanked out (they have a required flag), the overall validatedObservable on the containing observable does not update.

Simplified Jsfiddle example: http://jsfiddle.net/fbc0w39w/

Start with the linked jsFiddle example and reproduce the validation behavior using the Knockout mapping plugin. Trace how the individual required properties and the containing validatedObservable are connected; done means the containing validation state updates when a mapped property becomes invalid.

Written by the indexing model from the issue text.