Hill stability limits for the K2-19 system. We assume M_⋆ = 0.9 M_⊙, the mutual inclination between the planets is 1 degree, and a_b/a_c is within 0.1 per cent of based on the planetary orbital period ratios. Eccentricites are measured in Jacobi coordinates. If K2-19 is Hill unstable, then the 3:2 MMR might act as a crucial protection mechanism to ensure the system’s long-term stability on the main sequence.