diff --git a/src/config/app.config.ts b/src/config/app.config.ts
index 52e593032..c12c2e171 100644
--- a/src/config/app.config.ts
+++ b/src/config/app.config.ts
@@ -7,7 +7,7 @@
 import { registerAs } from '@nestjs/config';
 import * as Joi from 'joi';
 import { Loglevel } from './loglevel.enum';
-import { buildErrorMessage, toArrayConfig } from './utils';
+import { buildErrorMessage, parseOptionalInt, toArrayConfig } from './utils';
 
 export interface AppConfig {
   domain: string;
@@ -46,11 +46,10 @@ export default registerAs('appConfig', () => {
     {
       domain: process.env.HD_DOMAIN,
       rendererOrigin: process.env.HD_RENDERER_ORIGIN,
-      port: parseInt(process.env.PORT) || undefined,
+      port: parseOptionalInt(process.env.PORT),
       loglevel: process.env.HD_LOGLEVEL,
       forbiddenNoteIds: toArrayConfig(process.env.HD_FORBIDDEN_NOTE_IDS, ','),
-      maxDocumentLength:
-        parseInt(process.env.HD_MAX_DOCUMENT_LENGTH) || undefined,
+      maxDocumentLength: parseOptionalInt(process.env.HD_MAX_DOCUMENT_LENGTH),
     },
     {
       abortEarly: false,
diff --git a/src/config/database.config.ts b/src/config/database.config.ts
index da437faf5..94b8a5802 100644
--- a/src/config/database.config.ts
+++ b/src/config/database.config.ts
@@ -7,7 +7,7 @@
 import * as Joi from 'joi';
 import { DatabaseDialect } from './database-dialect.enum';
 import { registerAs } from '@nestjs/config';
-import { buildErrorMessage } from './utils';
+import { buildErrorMessage, parseOptionalInt } from './utils';
 
 export interface DatabaseConfig {
   username: string;
@@ -62,7 +62,7 @@ export default registerAs('databaseConfig', () => {
       password: process.env.HD_DATABASE_PASS,
       database: process.env.HD_DATABASE_NAME,
       host: process.env.HD_DATABASE_HOST,
-      port: parseInt(process.env.HD_DATABASE_PORT) || undefined,
+      port: parseOptionalInt(process.env.HD_DATABASE_PORT),
       storage: process.env.HD_DATABASE_STORAGE,
       dialect: process.env.HD_DATABASE_DIALECT,
     },
diff --git a/src/config/hsts.config.ts b/src/config/hsts.config.ts
index 0a1aa6916..de66729fc 100644
--- a/src/config/hsts.config.ts
+++ b/src/config/hsts.config.ts
@@ -6,7 +6,7 @@
 
 import * as Joi from 'joi';
 import { registerAs } from '@nestjs/config';
-import { buildErrorMessage } from './utils';
+import { buildErrorMessage, parseOptionalInt } from './utils';
 
 export interface HstsConfig {
   enable: boolean;
@@ -32,7 +32,7 @@ export default registerAs('hstsConfig', () => {
   const hstsConfig = hstsSchema.validate(
     {
       enable: process.env.HD_HSTS_ENABLE,
-      maxAgeSeconds: parseInt(process.env.HD_HSTS_MAX_AGE) || undefined,
+      maxAgeSeconds: parseOptionalInt(process.env.HD_HSTS_MAX_AGE),
       includeSubdomains: process.env.HD_HSTS_INCLUDE_SUBDOMAINS,
       preload: process.env.HD_HSTS_PRELOAD,
     },
diff --git a/src/config/utils.spec.ts b/src/config/utils.spec.ts
index 551aed0c5..6e24a37e2 100644
--- a/src/config/utils.spec.ts
+++ b/src/config/utils.spec.ts
@@ -6,6 +6,7 @@
 
 import {
   needToLog,
+  parseOptionalInt,
   replaceAuthErrorsWithEnvironmentVariables,
   toArrayConfig,
 } from './utils';
@@ -84,4 +85,12 @@ describe('config utils', () => {
       expect(needToLog(currentLevel, Loglevel.TRACE)).toBeTruthy();
     });
   });
+  describe('parseOptionalInt', () => {
+    it('returns undefined on undefined parameter', () => {
+      expect(parseOptionalInt(undefined)).toEqual(undefined);
+    });
+    it('correctly parses a string', () => {
+      expect(parseOptionalInt('42')).toEqual(42);
+    });
+  });
 });
diff --git a/src/config/utils.ts b/src/config/utils.ts
index cee786c09..f9f935af9 100644
--- a/src/config/utils.ts
+++ b/src/config/utils.ts
@@ -113,3 +113,10 @@ function transformLoglevelToInt(loglevel: Loglevel): number {
       return 1;
   }
 }
+
+export function parseOptionalInt(value?: string): number | undefined {
+  if (value === undefined) {
+    return undefined;
+  }
+  return parseInt(value);
+}