diff --git a/lib/http.js b/lib/http.js
index 7c6d753..2545961 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -861,6 +861,7 @@ function Agent(options) {
 
   this._settings = options.settings;
   this._log = (options.log || defaultLogger).child({ component: 'http' });
+  this._endpointKey = options.endpointKey;
   this.endpoints = {};
 
   // * Using an own HTTPS agent, because the global agent does not look at `NPN/ALPNProtocols` when
@@ -900,7 +901,7 @@ Agent.prototype.request = function request(options, callback) {
     request.on('response', callback);
   }
 
-  var key = [
+  var key = this._endpointKey || [
     !!options.plain,
     options.host,
     options.port