diff --git a/sc2/doc/devel/generate b/sc2/doc/devel/generate
index d9231ec7d..b3c399037 100644
--- a/sc2/doc/devel/generate
+++ b/sc2/doc/devel/generate
@@ -33,7 +33,8 @@ GENERATE_PLANETS
 Pre: the global variable pSolarSysState points to the relevant solar system.
 Pre: the RNG is initialised with a seed to be used for the generation.
      In practice, this seed is generated from the HyperSpace coordinates
-     of the solar system (which are hardcoded in sc2code/plandata.c).
+     of the solar system (which are hardcoded in sc2code/plandata.c),
+     followed by exactly one call to TFB_Random().
 Post: the RNG is in an undefined state.
 This function determines how many planets the system has, and fills in
 pSolarSysState->PlanetDesc[] for all planets, including the NumPlanets