The opening chapter of the original paperback edition of "Ringworld" featured Louis Wu teleporting eastward around the Earth in order to extend his birthday. Moving in this direction would, in fact, make local time later rather than earlier, so that Wu would soon arrive in the early morning of the next calendar day. Niven was "endlessly teased" about this error, which he corrected in subsequent printings to show Wu teleporting westward. In his dedication to "The Ringworld Engineers", Niven wrote, "If you own a first paperback edition of "Ringworld", it's the one with the mistakes in it. It's worth money."