diff --git a/src/services/inventoryService.ts b/src/services/inventoryService.ts
index 9d51f597..99d189d0 100644
--- a/src/services/inventoryService.ts
+++ b/src/services/inventoryService.ts
@@ -82,7 +82,7 @@ export const combineInventoryChanges = (InventoryChanges: IInventoryChanges, del
             for (const item of right) {
                 left.push(item);
             }
-        } else {
+        } else if (typeof delta[key] == "object") {
             console.assert(key.substring(-3) == "Bin");
             const left = InventoryChanges[key] as IBinChanges;
             const right: IBinChanges = delta[key];
@@ -93,6 +93,8 @@ export const combineInventoryChanges = (InventoryChanges: IInventoryChanges, del
                 left.Extra ??= 0;
                 left.Extra += right.Extra;
             }
+        } else {
+            logger.warn(`inventory change not merged: ${key}`);
         }
     }
 };
@@ -477,7 +479,11 @@ export const updateSlots = async (accountId: string, slotName: SlotNames, slotAm
     await inventory.save();
 };
 
-export const updateCurrency = async (price: number, usePremium: boolean, accountId: string) => {
+export const updateCurrency = async (
+    price: number,
+    usePremium: boolean,
+    accountId: string
+): Promise<IInventoryChanges> => {
     if (usePremium ? config.infinitePlatinum : config.infiniteCredits) {
         return {};
     }
diff --git a/src/types/purchaseTypes.ts b/src/types/purchaseTypes.ts
index 93725cee..83e5fb0d 100644
--- a/src/types/purchaseTypes.ts
+++ b/src/types/purchaseTypes.ts
@@ -17,7 +17,13 @@ export interface IPurchaseParams {
     UseFreeFavor?: boolean; // for Source 2
 }
 
-export type IInventoryChanges = Record<string, IBinChanges | object[]>;
+export type IInventoryChanges = {
+    [_ in SlotNames]?: IBinChanges;
+} & {
+    RegularCredits?: number;
+    PremiumCredits?: number;
+    PremiumCreditsFree?: number;
+} & Record<string, IBinChanges | number | object[]>;
 
 export interface IPurchaseResponse {
     InventoryChanges: IInventoryChanges;