Found the page.

"Here is another story illustrating Louis’s extreme dread of death. It seems that, being so superstitious, he never failed to consult all the astrologers he could, although he sometimes amused himself by making their predictions fail if it lay in his power to do so. An astrologer once came to court and predicted things which so enraged the king that he angrily resolved to put this man to death. In his hypocritical way, however, he slyly remarked: “You pretend to be very clever, and to be able to foretell the fate of others. Now, tell me your own fate and how much longer you have to live.”

The astrologer, perceiving his design, cleverly replied: “I shall die just three days before your Majesty.” This shrewd answer actually saved the man’s life, for after such a prediction the king was very careful not to do anything which, by shortening the astrologer’s days, might perchance hasten his own end."

EDIT: either this is the wrong bit or the title is indeed misleading.