diff --git a/src/babel/traversal/index.js b/src/babel/traversal/index.js
index 6a8a59898c..58f854f0b9 100644
--- a/src/babel/traversal/index.js
+++ b/src/babel/traversal/index.js
@@ -51,7 +51,7 @@ const CLEAR_KEYS = [
 traverse.clearNode = function (node) {
   for (var i = 0; i < CLEAR_KEYS.length; i++) {
     let key = CLEAR_KEYS[i];
-    if (node[key] != null) node[key] = null;
+    if (node[key] != null) node[key] = undefined;
   }
 };