diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 23a239d5c6..a1c97c3686 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -245,7 +245,7 @@ exports.parse = function (opts, code, callback) {
         message += frame;
       }
 
-      err.stack   = err.stack.replace(err.message, message);
+      if (err.stack) err.stack = err.stack.replace(err.message, message);
       err.message = message;
     }