diff --git a/src/client/http.js b/src/client/http.js
index 5244492..5dc73e2 100644
--- a/src/client/http.js
+++ b/src/client/http.js
@@ -32,8 +32,8 @@ function byteArrayToLong(/*byte[]*/byteArray) {
 
 class ApiClient {
 
-  constructor() {
-    this.apiUrl = process.env.API_URL;
+  constructor(apiUrl) {
+    this.apiUrl = apiUrl || process.env.API_URL;
     this.signer = null;
   }