diff --git a/src/services/inventoryService.ts b/src/services/inventoryService.ts
index 9d51f597..60acf7e6 100644
--- a/src/services/inventoryService.ts
+++ b/src/services/inventoryService.ts
@@ -85,7 +85,7 @@ export const combineInventoryChanges = (InventoryChanges: IInventoryChanges, del
         } else {
             console.assert(key.substring(-3) == "Bin");
             const left = InventoryChanges[key] as IBinChanges;
-            const right: IBinChanges = delta[key];
+            const right: IBinChanges = delta[key] as IBinChanges;
             left.count += right.count;
             left.platinum += right.platinum;
             left.Slots += right.Slots;
diff --git a/src/types/purchaseTypes.ts b/src/types/purchaseTypes.ts
index 93725cee..67b96419 100644
--- a/src/types/purchaseTypes.ts
+++ b/src/types/purchaseTypes.ts
@@ -17,7 +17,9 @@ export interface IPurchaseParams {
     UseFreeFavor?: boolean; // for Source 2
 }
 
-export type IInventoryChanges = Record<string, IBinChanges | object[]>;
+export type IInventoryChanges = {
+    [_ in SlotNames]?: IBinChanges;
+} & Record<string, IBinChanges | number | object[]>;
 
 export interface IPurchaseResponse {
     InventoryChanges: IInventoryChanges;