diff --git a/app/ecs/components/inventory.js b/app/ecs/components/inventory.js
index 872dfb1..d9c7368 100644
--- a/app/ecs/components/inventory.js
+++ b/app/ecs/components/inventory.js
@@ -109,8 +109,9 @@ class ItemProxy {
       instance.clear(this.slot);
     }
     else {
+      const difference = qty - instance.slots[this.slot].qty;
       instance.slots[this.slot].qty = qty;
-      this.Component.markChange(instance.entity, 'qtyUpdated', {[this.slot]: qty});
+      this.Component.markChange(instance.entity, 'qtyUpdated', {[this.slot]: difference});
     }
   }
   get source() {
@@ -138,7 +139,7 @@ export default class Inventory extends Component {
       }
       if (qtyUpdated) {
         for (const slot in qtyUpdated) {
-          slots[slot].qty = qtyUpdated[slot];
+          slots[slot].qty += qtyUpdated[slot];
         }
       }
       if (swapped) {
@@ -187,7 +188,7 @@ export default class Inventory extends Component {
         for (let slot = 1; slot < 11; ++slot) {
           if (slots[slot]?.source === stack.source) {
             slots[slot].qty += stack.qty;
-            Component.markChange(this.entity, 'qtyUpdated', {[slot]: slots[slot].qty});
+            Component.markChange(this.entity, 'qtyUpdated', {[slot]: stack.qty});
             return;
           }
         }
@@ -195,8 +196,8 @@ export default class Inventory extends Component {
           if (!slots[slot]) {
             slots[slot] = stack;
             this.$$items[slot] = new ItemProxy(Component, this, slot);
-            await this.$$items[slot].load(stack.source);
             Component.markChange(this.entity, 'given', {[slot]: slots[slot]});
+            await this.$$items[slot].load(stack.source);
             return;
           }
         }
@@ -233,10 +234,6 @@ export default class Inventory extends Component {
   mergeDiff(original, update) {
     const merged = {
       ...original,
-      qtyUpdated: {
-        ...original.qtyUpdated,
-        ...update.qtyUpdated,
-      },
       cleared: {
         ...original.cleared,
         ...update.cleared,
@@ -250,6 +247,14 @@ export default class Inventory extends Component {
         ...(update.swapped || []),
       ],
     };
+    if (update.qtyUpdated) {
+      if (!merged.qtyUpdated) {
+        merged.qtyUpdated = {};
+      }
+      for (const slot in update.qtyUpdated) {
+        merged.qtyUpdated[slot] = (merged.qtyUpdated[slot] ?? 0) + update.qtyUpdated[slot];
+      }
+    }
     return merged;
   }
   static properties = {