diff --git a/lib/_http_agent.js b/lib/_http_agent.js
index 8bc74c9cd43327..13bd5e9832d36e 100644
--- a/lib/_http_agent.js
+++ b/lib/_http_agent.js
@@ -252,8 +252,7 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
   if (options.socketPath)
     options.path = options.socketPath;
 
-  if (!options.servername && options.servername !== '')
-    options.servername = calculateServerName(options, req);
+  normalizeServerName(options, req);
 
   const name = this.getName(options);
   if (!this.sockets[name]) {
@@ -313,8 +312,7 @@ Agent.prototype.createSocket = function createSocket(req, options, cb) {
   if (options.socketPath)
     options.path = options.socketPath;
 
-  if (!options.servername && options.servername !== '')
-    options.servername = calculateServerName(options, req);
+  normalizeServerName(options, req);
 
   const name = this.getName(options);
   options._agentKey = name;
@@ -340,6 +338,11 @@ Agent.prototype.createSocket = function createSocket(req, options, cb) {
     oncreate(null, newSocket);
 };
 
+function normalizeServerName(options, req) {
+  if (!options.servername && options.servername !== '')
+    options.servername = calculateServerName(options, req);
+}
+
 function calculateServerName(options, req) {
   let servername = options.host;
   const hostHeader = req.getHeader('host');