diff --git a/lib/net.js b/lib/net.js
index e683101f5b1336..0554f3a69f8184 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -429,7 +429,7 @@ Stream.prototype._writeOut = function (data, encoding) {
       allocNewPool();
     }
 
-    if (encoding == 'utf8' || encoding == 'utf-8') {
+    if (!encoding || encoding == 'utf8' || encoding == 'utf-8') {
       // default to utf8
       bytesWritten = pool.write(data, 'utf8', pool.used);
       charsWritten = Buffer._charsWritten;