diff --git a/lib/_stream_transform.js b/lib/_stream_transform.js
index eec442226252af..9c24394b7d88fa 100644
--- a/lib/_stream_transform.js
+++ b/lib/_stream_transform.js
@@ -58,6 +58,7 @@ function TransformState(stream) {
   this.transforming = false;
   this.writecb = null;
   this.writechunk = null;
+  this.writeencoding = null;
 }
 
 function afterTransform(stream, er, data) {