diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/container/ContainerHelpers.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/container/ContainerHelpers.kt
index ad2c35539..c50cd7b5c 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/container/ContainerHelpers.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/container/ContainerHelpers.kt
@@ -7,6 +7,7 @@ import it.unimi.dsi.fastutil.ints.IntCollection
 import it.unimi.dsi.fastutil.ints.IntIterable
 import it.unimi.dsi.fastutil.ints.IntIterator
 import it.unimi.dsi.fastutil.ints.IntList
+import it.unimi.dsi.fastutil.ints.IntOpenHashSet
 import it.unimi.dsi.fastutil.ints.IntSet
 import it.unimi.dsi.fastutil.objects.Object2ObjectFunction
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenCustomHashMap
@@ -324,7 +325,7 @@ fun Container.sortWithIndices(sortedSlots: IntCollection) {
 	if (sortedSlots.isEmpty() || isEmpty)
 		return
 
-	val seen = IntAVLTreeSet()
+	val seen = IntOpenHashSet()
 	val valid = ArrayList<IContainerSlot>()
 
 	val iterator = sortedSlots.intIterator()