diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traverse/index.js
index 08a71bb35d..3985c421b2 100644
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -77,6 +77,8 @@ traverse.removeProperties = function (tree) {
   var clear = function (node) {
     delete node.tokens;
     delete node.range;
+    delete node.start;
+    delete node.end;
     delete node.loc;
   };