diff --git a/apps/api/src/app/portfolio/portfolio.service.ts b/apps/api/src/app/portfolio/portfolio.service.ts
index bb8ad2130..cc6d57954 100644
--- a/apps/api/src/app/portfolio/portfolio.service.ts
+++ b/apps/api/src/app/portfolio/portfolio.service.ts
@@ -24,6 +24,7 @@ import { RegionalMarketClusterRiskNorthAmerica } from '@ghostfolio/api/models/ru
 import { BenchmarkService } from '@ghostfolio/api/services/benchmark/benchmark.service';
 import { DataProviderService } from '@ghostfolio/api/services/data-provider/data-provider.service';
 import { ExchangeRateDataService } from '@ghostfolio/api/services/exchange-rate-data/exchange-rate-data.service';
+import { ExchangeRatesByCurrency } from '@ghostfolio/api/services/exchange-rate-data/interfaces/exchange-rate-data.interface';
 import { I18nService } from '@ghostfolio/api/services/i18n/i18n.service';
 import { ImpersonationService } from '@ghostfolio/api/services/impersonation/impersonation.service';
 import { SymbolProfileService } from '@ghostfolio/api/services/symbol-profile/symbol-profile.service';
@@ -1648,9 +1649,7 @@ export class PortfolioService {
     value
   }: {
     cashDetails: CashDetails;
-    exchangeRatesByCurrency: Awaited<
-      ReturnType<ExchangeRateDataService['getExchangeRatesByCurrency']>
-    >;
+    exchangeRatesByCurrency: ExchangeRatesByCurrency;
     userCurrency: string;
     value: Big;
   }) {
diff --git a/apps/api/src/services/exchange-rate-data/exchange-rate-data.service.ts b/apps/api/src/services/exchange-rate-data/exchange-rate-data.service.ts
index 433547c94..42551a3e2 100644
--- a/apps/api/src/services/exchange-rate-data/exchange-rate-data.service.ts
+++ b/apps/api/src/services/exchange-rate-data/exchange-rate-data.service.ts
@@ -26,6 +26,8 @@ import {
 import { isNumber } from 'lodash';
 import ms from 'ms';
 
+import { ExchangeRatesByCurrency } from './interfaces/exchange-rate-data.interface';
+
 @Injectable()
 export class ExchangeRateDataService {
   private currencies: string[] = [];
@@ -58,7 +60,7 @@ export class ExchangeRateDataService {
     endDate?: Date;
     startDate: Date;
     targetCurrency: string;
-  }) {
+  }): Promise<ExchangeRatesByCurrency> {
     if (!startDate) {
       return {};
     }
diff --git a/apps/api/src/services/exchange-rate-data/interfaces/exchange-rate-data.interface.ts b/apps/api/src/services/exchange-rate-data/interfaces/exchange-rate-data.interface.ts
new file mode 100644
index 000000000..8e0d2c0d4
--- /dev/null
+++ b/apps/api/src/services/exchange-rate-data/interfaces/exchange-rate-data.interface.ts
@@ -0,0 +1,5 @@
+export interface ExchangeRatesByCurrency {
+  [currency: string]: {
+    [dateString: string]: number;
+  };
+}