diff --git a/app/ecs/components/inventory.js b/app/ecs/components/inventory.js
index 633efb1..4694787 100644
--- a/app/ecs/components/inventory.js
+++ b/app/ecs/components/inventory.js
@@ -194,6 +194,12 @@ export default class Inventory extends Component {
         const tmp = [$$items[l], slots[l]];
         [$$items[l], slots[l]] = [$$items[r], slots[r]];
         [$$items[r], slots[r]] = tmp;
+        if (undefined === slots[l]) {
+          delete slots[l];
+        }
+        if (undefined === slots[r]) {
+          delete slots[r];
+        }
         Component.markChange(this.entity, 'swapped', [[l, r]]);
       }
     }