diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
index bc534ca16..8532889c8 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
@@ -322,6 +322,7 @@ export class RoaiPortfolioCalculator extends PortfolioCalculator {
 
     // Add a synthetic order at the start and the end date
     orders.push({
+      currency: undefined,
       date: startDateString,
       fee: new Big(0),
       feeInBaseCurrency: new Big(0),
@@ -337,6 +338,7 @@ export class RoaiPortfolioCalculator extends PortfolioCalculator {
     });
 
     orders.push({
+      currency: undefined,
       date: endDateString,
       fee: new Big(0),
       feeInBaseCurrency: new Big(0),
@@ -378,6 +380,7 @@ export class RoaiPortfolioCalculator extends PortfolioCalculator {
         }
       } else {
         orders.push({
+          currency: undefined,
           date: dateString,
           fee: new Big(0),
           feeInBaseCurrency: new Big(0),
diff --git a/apps/api/src/app/portfolio/interfaces/portfolio-order.interface.ts b/apps/api/src/app/portfolio/interfaces/portfolio-order.interface.ts
index 96e116e9a..5aeab7543 100644
--- a/apps/api/src/app/portfolio/interfaces/portfolio-order.interface.ts
+++ b/apps/api/src/app/portfolio/interfaces/portfolio-order.interface.ts
@@ -1,7 +1,9 @@
 import { Activity } from '@ghostfolio/common/interfaces';
 
-export interface PortfolioOrder extends Pick<Activity, 'tags' | 'type'> {
-  currency?: string;
+export interface PortfolioOrder extends Pick<
+  Activity,
+  'currency' | 'tags' | 'type'
+> {
   date: string;
   fee: Big;
   feeInBaseCurrency: Big;