NSF Flow port stats do not show for mininet OF10

These are the steps:

start mininet with: sudo mn --controller=remote,ip=127.0.0.1 --topo tree,2

Pull port stats:
http://127.0.0.1:8080/controller/nb/v2/statistics/default/port

No ports are shown on the response body:

<list>
<portStatistics>
<node>
<id>00:00:00:00:00:00:00:02</id>
<type>OF</type>
</node>
</portStatistics>
<portStatistics>
<node>
<id>00:00:00:00:00:00:00:03</id>
<type>OF</type>
</node>
</portStatistics>
<portStatistics>
<node>
<id>00:00:00:00:00:00:00:01</id>
<type>OF</type>
</node>
</portStatistics>
</list>