File.preventBackup Not Working

Hi,

I'm possibly using this property in the wrong manner, but I couldn't find any examples. In the startup of my mobile app, I'm doing something like:

var cacheDir:File = File.applicationStorageDirectory.resolvePath("cache");

cacheDir.preventBackup = true;

However, on iOS this directory is still getting backed up. Throughout the mobile app I am referencing File.applicationStorageDirectory.resolvePath("cache").url to open and write files. Should I instead be referencing the cacheDir variable in order for this to work? I wouldn't think it'd make a difference since both point to the same location.

thx