View.asMap() causes a ClassCastException in Apex runner

See code sample in https://stackoverflow.com/questions/46982827/error-when-using-side-input-withsideinputs-method-not-accepting-kv-type-as-inp?noredirect=1#comment81040223_46982827

The error does not happen in direct runner. It also does not happen if I replace View.asMap() with View.asIterable (and do the appropriate type changes)