Effect of limb-darkening on stellar contamination factor and observed transit depth for stars of different spectral types. Top: illustration of the stellar disc with a single spot at four different positions, i.e. at different stellar rotation phases. Bottom: corresponding stellar contamination spectra for F5V, G5V, K5V, and M5V stars with LD (solid) and without LD (dashed). The secondary y-axis represents the change in transit depth due to stellar contamination assuming a planet with a uniform transit depth of 1% at all wavelengths.