diff --git a/inferium-harvester.lua b/inferium-harvester.lua
index def6c4b..1d73fee 100644
--- a/inferium-harvester.lua
+++ b/inferium-harvester.lua
@@ -27,6 +27,18 @@ local localPlan = nil
 
 -- UTILS
 
+local function sizeof(t)
+  if not t then
+    return 0
+  end
+
+  local size = 0
+  for k,v in pairs(t) do
+    size = size + 1
+  end
+  return size
+end
+
 local function difference(a, b)
   local aa = {}
 
@@ -419,15 +431,15 @@ local function replantProcedure()
   local seedsToRemove = difference(localPlan, remotePlan)
   local seedsToPlant = difference(remotePlan, localPlan)
 
-  if #seedsToRemove > 0 then
-    print('nb seeds to remove: ' .. #seedsToRemove)
+  if sizeof(seedsToRemove) > 0 then
+    print('nb seeds to remove: ' .. sizeof(seedsToRemove))
     removeSeeds(seedsToRemove)
   else
     print('no seeds to remove')
   end
 
-  if #seedsToPlant > 0 then
-    print('nb seeds to plants: ' .. #seedsToPlant)
+  if sizeof(seedsToPlant) > 0 then
+    print('nb seeds to plants: ' .. sizeof(seedsToPlant))
     retrieveSeeds(seedsToPlant)
     replantSeeds()
   else