Evolution of the orbital distance of pebbles as they drift through a disc with an embedded 25 M_E planet (top) and an embedded 30 M_E planet (bottom). Even though the planet has generated a pressure bump outside of its orbit (maximum at r = 1.123, see Fig. 1), small pebbles with τ_f < 0.005 can drift through the pressure bump for the 25 M_E planet, while the Stokes number of the particles has to be an order of magnitude smaller to drift through the pressure bump generated by the 30 M_E planet.