diff --git a/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemCollector.java b/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemCollector.java
index c39494e8..8ad85ca7 100644
--- a/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemCollector.java
+++ b/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemCollector.java
@@ -73,7 +73,7 @@ public class ItemCollector<T> {
                 items.addTo(def, stack.getCount());
             }
         });
-        iterator.afterPopulate(count.get());
+        iterator.afterPopulate(container, count.get());
         if (mergedResult != null && !iterator.isFinished()) {
             updateCollectingProgress(mergedResult.getFirst());
             return mergedResult;
diff --git a/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemIterator.java b/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemIterator.java
index 4d65e9a8..08ebca52 100644
--- a/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemIterator.java
+++ b/leaves-server/src/main/java/org/leavesmc/leaves/protocol/jade/util/ItemIterator.java
@@ -15,6 +15,7 @@ public abstract class ItemIterator<T> {
     protected final int fromIndex;
     protected boolean finished;
     protected int currentIndex;
+    protected float progress;
 
     protected ItemIterator(Function<Object, @Nullable T> containerFinder, int fromIndex) {
         this.containerFinder = containerFinder;
@@ -35,16 +36,19 @@ public abstract class ItemIterator<T> {
 
     public abstract Stream<ItemStack> populate(T container);
 
+    protected abstract int getSlotCount(T container);
+
     public void reset() {
         currentIndex = fromIndex;
         finished = false;
     }
 
-    public void afterPopulate(int count) {
+    public void afterPopulate(T container, int count) {
         currentIndex += count;
         if (count == 0 || currentIndex >= 10000) {
             finished = true;
         }
+        progress = (float) (currentIndex - fromIndex) / (getSlotCount(container) - fromIndex);
     }
 
     public float getCollectingProgress() {
@@ -52,14 +56,11 @@ public abstract class ItemIterator<T> {
     }
 
     public static abstract class SlottedItemIterator<T> extends ItemIterator<T> {
-        protected float progress;
 
         public SlottedItemIterator(Function<Object, @Nullable T> containerFinder, int fromIndex) {
             super(containerFinder, fromIndex);
         }
 
-        protected abstract int getSlotCount(T container);
-
         protected abstract ItemStack getItemInSlot(T container, int slot);
 
         @Override
@@ -70,7 +71,6 @@ public abstract class ItemIterator<T> {
                 toIndex = slotCount;
                 finished = true;
             }
-            progress = (float) (currentIndex - fromIndex) / (slotCount - fromIndex);
             return IntStream.range(currentIndex, toIndex).mapToObj(slot -> getItemInSlot(container, slot));
         }