From a363ac0781264fce0ac57d9f23b15999edc05463 Mon Sep 17 00:00:00 2001
From: Craig Cavalier <craigcav@gmail.com>
Date: Tue, 14 Jul 2015 11:06:48 -0400
Subject: [PATCH] only apply drain listener when callback provided

---
 lib/zlib.js | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/zlib.js b/lib/zlib.js
index a85e8efb5181..64135ffece45 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -450,9 +450,11 @@ Zlib.prototype.flush = function(kind, callback) {
       this.once('end', callback);
   } else if (ws.needDrain) {
     var self = this;
-    this.once('drain', function() {
-      self.flush(callback);
-    });
+    if (callback) {
+      this.once('drain', function() {
+        self.flush(callback);
+      });
+    }
   } else {
     this._flushFlag = kind;
     this.write(new Buffer(0), '', callback);