diff --git a/js/base/Exchange.js b/js/base/Exchange.js
index e4075a27af6fe..2d4034643f7cd 100644
--- a/js/base/Exchange.js
+++ b/js/base/Exchange.js
@@ -93,6 +93,8 @@ module.exports = class Exchange {
         this.substituteCommonCurrencyCodes = true  // reserved
         this.parseBalanceFromOpenOrders    = false // some exchanges return balance updates from order API endpoints
 
+        this.fetchImplementation = fetch
+
         this.timeout          = 10000 // milliseconds
         this.verbose          = false
         this.debug            = false
@@ -275,7 +277,7 @@ module.exports = class Exchange {
         this.executeRestRequest = function (url, method = 'GET', headers = undefined, body = undefined) {
 
             let promise =
-                fetch (url, { 'method': method, 'headers': headers, 'body': body, 'agent': this.tunnelAgent || null, timeout: this.timeout})
+                this.fetchImplementation (url, { 'method': method, 'headers': headers, 'body': body, 'agent': this.tunnelAgent || null, timeout: this.timeout})
                     .catch (e => {
                         if (isNode)
                             throw new ExchangeNotAvailable ([ this.id, method, url, e.type, e.message ].join (' '))