diff --git a/inferium-harvester.lua b/inferium-harvester.lua
index 1d73fee..8542139 100644
--- a/inferium-harvester.lua
+++ b/inferium-harvester.lua
@@ -40,19 +40,15 @@ local function sizeof(t)
 end
 
 local function difference(a, b)
-  local aa = {}
+  local ai = {}
+  local r = {}
 
-  for k,v in pairs(a) do aa[v]=true end
-  for k,v in pairs(b) do aa[v]=nil end
-
-  local ret = {}
-  local n = 0
-
-  for k,v in pairs(a) do
-      if aa[v] then n=n+1 ret[n]=v end
+  for k,v in pairs(a) do r[k] = v; ai[v]=true end
+  for k,v in pairs(b) do
+      if ai[v]~=nil then   r[k] = nil   end
   end
 
-  return ret
+  return r
 end
 
 local function shallowClone(t)