The detection of faults in software systems can be effectively enhanced by model-based mutation testing. The efficiency of this technique is hindered when mutants are equivalent to the original system model, making them not useful.

Model-based mutation testing applied to real-time systems modelled as timed games has been recently investigated, providing guidelines for statically avoiding equivalent mutants.

In this paper, we recast this problem to the framework of parametric timed games. We prove a correspondence between theoretical results for detecting equivalent mutants in timed games and the property of monotonicity holding on a sub-class of parametric timed games called L/U parametric timed games. The presented results simplify the theory on the detection of equivalent mutants in timed games whilst improving the expressiveness of a known decidable fragment of parametric timed games for which monotonicity holds.