diff --git a/client-v3/src/js/platform/browser.ts b/client-v3/src/js/platform/browser.ts
index 1ac2a2ea..84d05d71 100644
--- a/client-v3/src/js/platform/browser.ts
+++ b/client-v3/src/js/platform/browser.ts
@@ -10,7 +10,7 @@
  * @returns {string} Base URL (e.g., "http://localhost:8080")
  */
 export function baseURL(): string {
-  return `${window.location.protocol}//${window.location.hostname}:${window.location.port}`;
+  return `${window.location.protocol}//${window.location.hostname}${window.location.port ? ':' + window.location.port : ''}`;
 }
 
 export function makeURL(path: string): string {
diff --git a/client/src/js/platform/browser.test.ts b/client/src/js/platform/browser.test.ts
index 79edf07e..21b31990 100644
--- a/client/src/js/platform/browser.test.ts
+++ b/client/src/js/platform/browser.test.ts
@@ -39,7 +39,7 @@ describe('browser.js', () => {
       window.location.port = '';
 
       const result = baseURL();
-      expect(result).toBe('http://localhost:');
+      expect(result).toBe('http://localhost');
     });
   });
 
diff --git a/client/src/js/platform/browser.ts b/client/src/js/platform/browser.ts
index 1ac2a2ea..84d05d71 100644
--- a/client/src/js/platform/browser.ts
+++ b/client/src/js/platform/browser.ts
@@ -10,7 +10,7 @@
  * @returns {string} Base URL (e.g., "http://localhost:8080")
  */
 export function baseURL(): string {
-  return `${window.location.protocol}//${window.location.hostname}:${window.location.port}`;
+  return `${window.location.protocol}//${window.location.hostname}${window.location.port ? ':' + window.location.port : ''}`;
 }
 
 export function makeURL(path: string): string {