Two planets locked in resonance in a circumstellar disk can produce a unique signature on the distribution of the nearby dust. According to Marzari et al. (2018), the outward migration of the planets cause a decoupling between the gas and dust gaps and an overdense ring at the outer border of the common gap. Those computations did not take into account the potential diffusion due to gas turbulence and to the back-reaction of the dust on the gas. New simulations have been performed by using the multifluid version of fargo3D (Benítez-Llambay et al., 2019). Preliminary results indicate that neither diffusion nor back-reaction significantly affect the dust distribution, even though the back-reaction of the dust can affect the migration of the planets.