The condition of being unable to make up for it is a permanent inability that does not allow for the possibility of being able to do so for the rest of one's life; thus, it is only obligatory on the elderly. Therefore, there is no compensation for the sick or the traveler, nor for the pregnant or nursing woman. Anyone who breaks their fast due to a valid excuse that allows for the possibility of being able to fast later does not have to make up for it, due to the absence of the condition, which is the ongoing inability. This is because compensation is a substitute for making up, and the ability to fulfill the original obligation prevents resorting to a substitute, as is the case with all substitutes in relation to their originals. Therefore, if an elderly person compensates and then becomes able to fast, the compensation becomes invalid. See: Bada'i al-Sanai' 2: 104.