Unique Visitors reported zero in export, but not in graph

In the GUI I’ve selected a date range that spans slightly over 2 months. When I look at the number of Unique Visitors in the graphs of either the ‘Visits Over Time’ or the ‘Visits Overview (with graph)’ widgets, I get a nice plot of their its evolution over time (per day).

But when I export the data (this aggregates for the selected date range), the ‘nb_uniq_visitors’ consistently gets reported as 0.

When I use a period of a single day, I do get the results I expect…

Any idea why date range isn’t reporting the nb_uniq_visitors correctly?
Is there a way I can get the number of Unique Visitors when I select a date range for the period?

Are you using 2.2.2 ? please try with this version as we’ve fixed a related bug