diff --git a/lib/request.js b/lib/request.js
index 372a9915e9..476961fae7 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -399,17 +399,17 @@ defineGetter(req, 'path', function path() {
  * address, the "X-Forwarded-Host" header field will
  * be trusted.
  *
- * @return {String}
+ * @return {(String|undefined)}
  * @public
  */
 
-defineGetter(req, 'host', function host(){
-  var trust = this.app.get('trust proxy fn');
-  var val = this.get('X-Forwarded-Host');
+defineGetter(req, 'host', function() {
+  const trust = this.app.get('trust proxy fn');
+  let val = this.get('X-Forwarded-Host');
 
   if (!val || !trust(this.connection.remoteAddress, 0)) {
     val = this.get('Host');
-  } else if (val.indexOf(',') !== -1) {
+  } else if (val.includes(',')) {
     // Note: X-Forwarded-Host is normally only ever a
     //       single value, but this is to be safe.
     val = val.substring(0, val.indexOf(',')).trimRight()
@@ -418,6 +418,7 @@ defineGetter(req, 'host', function host(){
   return val || undefined;
 });
 
+
 /**
  * Parse the "Host" header field to a hostname.
  *