'group-by' single column gives unexpected group name

[behrica]

(-> articles
    (tc/group-by  :output-type)
    (tc/aggregate {:num-articles tc/row-count}))

|                         :$group-name | :num-articles |
|--------------------------------------|--------------:|

I would expect the group name to be ":output-type"

It does work , if I use [:output-type] as grouping

[genmeblog]

Yes, it works now like that. I need to remind why. If there is no any reason I will make a change.