Why the biz day convention of OIS Rate helper is hard coded as Modified Following in QL?

Question

I am using QuantLib OIS Rate Helpers, and traced schedule creation back to the following function, and noticed that the business convention is hard coded as MF. Is the biz day convention hard coded because OIS is always MF. Or anyway I can create schedule by argument?

 MakeOIS::operator ext::shared_ptr<OvernightIndexedSwap>() const {
...
     Schedule schedule(startDate, endDate,
                       Period(paymentFrequency_),
                       calendar_,
                       ModifiedFollowing,
                       ModifiedFollowing,
                       rule_,
                       usedEndOfMonth);
     ...
 }