diff --git a/src/WebSocket.php b/src/WebSocket.php
index bf0ebc8..0e9f7f6 100644
--- a/src/WebSocket.php
+++ b/src/WebSocket.php
@@ -130,6 +130,7 @@ public function send($msg) {
 
     public function close($code = 1000, $reason = '') {
         $frame = new Frame(pack('n', $code) . $reason, true, Frame::OP_CLOSE);
+        $frame->maskPayload();
         $this->_stream->write($frame->getContents());
 
         $closeFn = $this->_close;