diff --git a/src/simulation.h b/src/simulation.h
index 59bf24d..276d696 100644
--- a/src/simulation.h
+++ b/src/simulation.h
@@ -57,6 +57,7 @@ double calculate_soi_radius(CelestialBody* body, CelestialBody* parent);
 
 void compute_global_coordinates(SimulationState* sim);
 
+// FIXME: don't need to be interface functions
 // Simulation update helper functions
 void update_bodies_physics(SimulationState* sim);
 void update_spacecraft_physics(SimulationState* sim);