From ed300a4c033d48f55575dc2654ff0a19b2960fee Mon Sep 17 00:00:00 2001
From: Nathan Rajlich <nathan@tootallnate.net>
Date: Tue, 27 Jun 2017 16:29:07 -0700
Subject: [PATCH] only set ALPNProtocols when the property does not already
 exist

I guess maybe you could do `ALPNProtocols: null` to opt-out
of this new behavior. Not sure if it's really necessary but hey.
---
 index.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index dd22ec64..3448b71d 100644
--- a/index.js
+++ b/index.js
@@ -41,8 +41,10 @@ function HttpsProxyAgent(opts) {
   proxy.host = proxy.hostname || proxy.host;
   proxy.port = +proxy.port || (this.secureProxy ? 443 : 80);
 
-  if (this.secureProxy) {
-    proxy.ALPNProtocols = proxy.ALPNProtocols || ['http 1.1']
+  // ALPN is supported by Node.js >= v5.
+  // attempt to negotiate http/1.1 for proxy servers that support http/2
+  if (this.secureProxy && !('ALPNProtocols' in proxy)) {
+    proxy.ALPNProtocols = ['http 1.1']
   }
 
   if (proxy.host && proxy.path) {