diff --git a/LuaLibs/BeamLib.lua b/LuaLibs/BeamLib.lua
index da1e6f6..c585685 100644
--- a/LuaLibs/BeamLib.lua
+++ b/LuaLibs/BeamLib.lua
@@ -734,7 +734,9 @@ end
 
 -------------------------------------------------------------------------------------------------------------
 function BeamLib.GetNzLimDownUp( b3Raw, vtN, vtOrtho)
-   if BD.C_SIMM then
+   if BD.GetNzLimDownUp then
+      return BD.GetNzLimDownUp( b3Raw, vtN, vtOrtho)
+   elseif BD.C_SIMM then
       return -0.484
    elseif BD.TURN then
       return -2