diff --git a/sim/gatedef.lua b/sim/gatedef.lua
index fde6a85..9f95253 100644
--- a/sim/gatedef.lua
+++ b/sim/gatedef.lua
@@ -26,6 +26,7 @@ function GateDefinition:new(objref, name, description, init, logic, input, globa
 		o.init = initfunc() or function()end
 	else
 		print("Error loading init func for ".. (name or ""))
+		print(init)
 	end
 	
 	local logicfunc = loadstring(tostring(logic))
@@ -41,6 +42,7 @@ function GateDefinition:new(objref, name, description, init, logic, input, globa
 		o.input = inputfunc() or function()end
 	else
 		print("Error loading input function for " .. (name or ""))
+		print(input)
 	end
 	
 	local globalfunc = loadstring(tostring(global))
@@ -48,6 +50,7 @@ function GateDefinition:new(objref, name, description, init, logic, input, globa
 		globalfunc()
 	else
 		print("Error loading global function for ".. (name or ""))
+		print(global)
 	end
 	
 	setmetatable(o, self)
diff --git a/sim/main.lua b/sim/main.lua
index 4910181..d9f9fc3 100644
--- a/sim/main.lua
+++ b/sim/main.lua
@@ -145,7 +145,10 @@ while 1 do
 				i = i + 4
 			elseif data[i] == "G" then
 				local objref = tonumber(data[i+1])
-				local definition = sim:getdefinitionbyref(tonumber(data[i+2])) or GateDefinition
+				local definition = sim:getdefinitionbyref(tonumber(data[i+2]))
+				
+				assert(definition, "No gate definition for objref "..objref)
+				
 				local position = vectotable(data[i+3])
 				local rotation = tonumber(data[i+4])
 				local gate = definition:constructgate(objref, position, rotation)