diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/container/slotted/SlottedContainer.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/container/slotted/SlottedContainer.kt
index 2f013f4d6..31a8b5795 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/container/slotted/SlottedContainer.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/container/slotted/SlottedContainer.kt
@@ -274,6 +274,7 @@ class SlottedContainer(
 					for ((item, slot) in items) {
 						if (slot in 0 until containerSize) {
 							slots[slot].item = item
+							bitmap[slot] = item.isNotEmpty
 						} else if (item.isNotEmpty) {
 							ItemStack.CODEC.encodeStart(provider.createSerializationContext(NbtOps.INSTANCE), item)
 								.ifError { LOGGER.warn("Unable to serialize 'lost' item: ${it.message()}") }
@@ -307,6 +308,7 @@ class SlottedContainer(
 
 				if (i in 0 until containerSize) {
 					slots[i].deserializeNBT(provider, element)
+					bitmap[i] = slots[i].isNotEmpty
 				} else {
 					lostItems.add(element)
 					this.provider = provider