SupplementaryMetricOptional is always null

I am trying to write some optional data to the leaderboard using Leaderboards.WriteEntryWithSupplementaryMetric

e.g. Leaderboards.WriteEntryWithSupplementaryMetric("scoreboard", Score, ExtraInfo , null, true)

But when I use GetEntries() to grab the score, supplementaryMetricOptional is always null. Is there any example of this working?