diff --git a/source/games/duke/src/player_r.cpp b/source/games/duke/src/player_r.cpp
index b2c7a0b9e..95472e6bf 100644
--- a/source/games/duke/src/player_r.cpp
+++ b/source/games/duke/src/player_r.cpp
@@ -596,7 +596,7 @@ static void shootrpg(DDukeActor* actor, int p, DVector3 pos, DAngle ang, int atw
 				ang = (aimed->spr.pos.XY() - pos.XY()).Angle();
 		}
 		else
-			zvel = ps[p].horizon.sum().Tan() * 40.5;
+			setFreeAimVelocity(vel, zvel, ps[p].horizon.sum(), 40.5);
 
 		if (atwith == RPG)
 			S_PlayActorSound(RPG_SHOOT, actor);