Load shift keying (LSK) is widely used in a wireless power transfer (WPT) system to backscatter secondary side information to the primary side. However, when the coupling coefficient ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> ) between the transmitter and the receiver coils is lower than a critical value ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">kDF</i> ), the demodulated LSK data may flip from '1' to '0' or '0' to '1', which is popularly known as coupling-dependent data flipping (CDDF). In this paper, the conditions leading to CDDF are analyzed. Parasitic components of the inductive link are included, and both matched and unmatched coupled resonators are analyzed and verified by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SPICE</i> simulations. An automatic carrier-frequency modulation scheme is proposed to prevent CDDF and is verified by measurement results.