diff --git a/lib/node-http-proxy/proxy-stream.js b/lib/node-http-proxy/proxy-stream.js
index 31dd2d3..19e0584 100644
--- a/lib/node-http-proxy/proxy-stream.js
+++ b/lib/node-http-proxy/proxy-stream.js
@@ -86,7 +86,11 @@ ProxyStream.prototype.start = function (req) {
     //
     // Process the `pReq` `pRes` when it's received.
     //
-    pRes.headers.connection = req.headers.connection || req.httpVersion === '1.0' ? 'close' : 'keep-alive';
+    if (req.httpVersion === '1.0') {
+      pRes.headers.connection = req.headers.connection || 'close';
+    } else if (!pRes.headers.connection) {
+      pRes.headers.connection = req.headers.connection || 'keep-alive';
+    }
 
     // Remove `Transfer-Encoding` header if client's protocol is HTTP/1.0
     // or if this is a DELETE request with no content-length header.