diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index b2859ea3d28..879e5ddb53f 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -686,7 +686,7 @@ Readable.prototype.unpipe = function(dest) {
   }
 
   // try to find the right one.
-  const index = state.pipes.indexOf(dest);
+  var index = state.pipes.indexOf(dest);
   if (index === -1)
     return this;