diff --git a/app/ecs-components/inventory.js b/app/ecs-components/inventory.js
index c639244..59311f3 100644
--- a/app/ecs-components/inventory.js
+++ b/app/ecs-components/inventory.js
@@ -2,8 +2,45 @@ import Schema from '@/ecs/schema.js';
 
 export default function(Component) {
   return class Inventory extends Component {
+    insertMany(entities) {
+      for (const [id, {slotChanged}] of entities) {
+        if (slotChanged) {
+          for (const slotIndex in slotChanged) {
+            this.get(id).slots[slotIndex] = {
+              ...this.get(id).slots[slotIndex],
+              ...slotChanged[slotIndex],
+            };
+          }
+        }
+      }
+      return super.insertMany(entities);
+    }
+    markChange(entityId, key, value) {
+      if ('slotChange' === key) {
+        const {index, change} = value;
+        return super.markChange(entityId, key, {[index]: change});
+      }
+      return super.markChange(entityId, key, value);
+    }
+    mergeDiff(original, update) {
+      if (update.slotChange) {
+        if (!original.slotChange) {
+          original.slotChange = {};
+        }
+        const merged = {};
+        for (const index in update.slotChange) {
+          merged[index] = {
+            ...original.slotChange[index],
+            ...update.slotChange[index],
+          };
+        }
+        return {slotChanged: merged};
+      }
+      return super.mergeDiff(original, update);
+    }
     instanceFromSchema() {
       const Instance = super.instanceFromSchema();
+      const Component = this;
       Instance.prototype.item = function (slot) {
         const {slots} = this;
         const instance = this;
@@ -12,12 +49,9 @@ export default function(Component) {
           if (slot === item.slotIndex) {
             const proxy = new Proxy(item, {
               set(target, property, value) {
-                const newSlots = [...slots];
-                newSlots[index] = {
-                  ...target,
-                  [property]: value,
-                };
-                instance.slots = newSlots;
+                target[property] = value;
+                const change = {[property]: value};
+                Component.markChange(instance.entity, 'slotChange', {index, change});
                 return true;
               },
             });
diff --git a/app/react-components/ui.jsx b/app/react-components/ui.jsx
index eaa44f8..a8014a3 100644
--- a/app/react-components/ui.jsx
+++ b/app/react-components/ui.jsx
@@ -144,13 +144,24 @@ export default function Ui({disconnected}) {
       if (localMainEntity === id) {
         if (payload.ecs[id].Inventory) {
           const newHotbarSlots = [...hotbarSlots];
-          payload.ecs[id].Inventory.slots
-            .forEach(({qty, slotIndex, source}) => {
+          const {slots, slotChanged} = payload.ecs[id].Inventory;
+          if (slotChanged) {
+            for (const slotIndex in slotChanged) {
               newHotbarSlots[slotIndex] = {
-                image: source + '/icon.png',
-                qty,
+                ...newHotbarSlots[slotIndex],
+                ...slotChanged[slotIndex],
               };
-            });
+            }
+          }
+          if (slots) {
+            slots
+              .forEach(({qty, slotIndex, source}) => {
+                newHotbarSlots[slotIndex] = {
+                  image: source + '/icon.png',
+                  qty,
+                };
+              });
+          }
           setHotbarSlots(newHotbarSlots);
         }
         if (payload.ecs[id].Wielder && 'activeSlot' in payload.ecs[id].Wielder) {