fi.SetTierFreeVersionID(mustGetUUID())
			// delete this version leading to a free version
			xl.DeleteVersion(fi)
			freeVersionIDs = append(freeVersionIDs, fi.TierFreeVersionID())
			allVersionIDs = append(allVersionIDs, fi.TierFreeVersionID())
		} else {
			versions = append(versions, fi)
			allVersionIDs = append(allVersionIDs, fi.VersionID)
		}
	}
	buf, err := xl.AppendTo(nil)
	if err != nil {