Upper mass limit for a fictitious outer planet in the planetary system around Qatar-1, based on timing and RV datasets, as a function of the orbital period of that planet, P_p. Configurations that are below the detection threshold of both techniques are placed in the grayed space of parameters, bounded by a continuous line. The dotted and dashed lines show detection limits for timing and RV techniques, respectively. Configurations with P_p/P_b< 1.5 were found to be unstable on a short timescale of the simulations.