Fullcalendar : minTime wrongly calculate fc-not-start

I am using the Fullcalendar library, scheduler module.

I use minTime properties and set it to: '06:00:00' inside of view definition (so that "day is not start with midnight").

But when I that, the elements that starts before 6h has a class fc-not-start even when they are in the middle of the calendar...

How to handle this?