Is it obligatory to make up for the vowed fast of the White Days if it coincides with menstruation, or is there no making up for a vow to fast?

Scholars have differed concerning a vow to fast specific days if menstruation or post-natal bleeding (nifas) occurs on those days. The Maliki and Shafi'i (the sound opinion) schools, and one narration from Ahmad, hold that neither making up the fast (qada') nor expiation (kaffarah) is required. The Hanbali school (their sound opinion) holds that making up the fast is required along with an expiation for breaking an oath. As for the Hanafis, another opinion from the Shafi'i school, and another narration from Ahmad, which is the most preferred view, only making up the fast is required. This is based on an analogy with obligatory fasts if they are prevented by a legitimate legal impediment. Accordingly, the days that coincided with menstruation or post-natal bleeding should be made up at another time.