Expected fractional flux enhancement anti-correlated with the QPO period for a flare in the Keplerian motion as a function of the orbital radius and the inclination angle. The flare must be located far away or the inclination must be low to ensure that this effect does not suppress the observed opposite trend. Amplitudes larger than  ~0.05 (above the continuous blue line) are highly improbable, and low inclination (below 10 deg) is required for a flare model.