diff --git a/sim/gatedef.lua b/sim/gatedef.lua
index d654ce2..203ea99 100644
--- a/sim/gatedef.lua
+++ b/sim/gatedef.lua
@@ -1,4 +1,6 @@
 
+local ffi = FFI or require("ffi")
+
 GateDefinition = {
 	ports = {},
 	logic = function(gate) end,