In any Havok4 simulator, rez a prim and paste this into a new script: default { state_entry() { llOwnerSay(llDumpList2String(llGetPrimitiveParams([PRIM_CAST_SHADOWS]),",")); llSetPrimitiveParams([PRIM_CAST_SHADOWS,1]); } } You'll get back: Object: llGetPrimitiveParams error: param 0 error, unknown parameter Object: Object: llSetPrimitiveParams error running rule #1: unknown rule. Works fine on the main. If PRIM_CAST_SHADOWS is being depreciated, please document the change in http://wiki.secondlife.com/wiki/LlGetPrimitiveParams and http://wiki.secondlife.com/wiki/LlSetPrimitiveParams . If this is otherwise unintended, please fix it