פירוש על קידושין 67:11

Rava points out another reason we might have thought women were liable for the sukkah—it falls on the fifteenth of the month, as does Pesah. Since women are obligated to eat matzah on Pesah which falls on the fifteenth of the month, so too they would be liable for sukkah which falls on the fifteenth of the month. This is why we need the midrash to teach that they are exempt.