va3 sensor history duration exception

H,

on VA3 when i try to debug in he simulator:

var historyDuration = new Time.Duration(60);
var hrIterator = SensorHistory.getHeartRateHistory({ :period => historyDuration });

gives me :

Unhandled Exception
UnexpectedTypeException: Expected an object of type Time.Duration
native function
native function


any idea ?

Marco