diff --git a/stackgroup.lua b/stackgroup.lua
index 28eed90..d769e4e 100644
--- a/stackgroup.lua
+++ b/stackgroup.lua
@@ -20,7 +20,7 @@ function prototype:defragment(chests)
     -- Find largest non-full stack
     for i=top,bottom,-1 do
         local entry = self[i]
-        if entry:getStack(chests).availableCount() ~= 0 then
+        if entry:getStack(chests):availableCount() ~= 0 then
             top = i
             break
         else
@@ -32,7 +32,7 @@ function prototype:defragment(chests)
         local topEntry = self[top]
         local bottomEntry = self[bottom]
 
-        local txCap = math.min(bottomEntry.count, topEntry:getStack(chests).availableCount())
+        local txCap = math.min(bottomEntry.count, topEntry:getStack(chests):availableCount())
         local tx = bottomEntry:getChest(chests):moveItemsTo(txCap, bottomEntry.slot, topEntry:getChest(chests), topEntry.slot)
 
         if tx ~= txCap then
@@ -51,7 +51,7 @@ function prototype:defragment(chests)
             bottom = bottom + 1
         end
 
-        if topEntry:getStack(chests).availableCount() == 0 then
+        if topEntry:getStack(chests):availableCount() == 0 then
             top = top - 1
             resultGroup[#resultGroup + 1] = topEntry
         end