diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index c580240c83..babf072a50 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -24,10 +24,6 @@ exports.isPattern = function (node) {
   return node.type === "ArrayPattern" || node.type === "ObjectPattern";
 };
 
-exports.formatJSON = function (obj) {
-  return JSON.stringify(obj, null, "  ");
-};
-
 exports.isAbsolute = function (loc) {
   if (!loc) return false;
   if (loc[0] === "/") return true; // unix
@@ -203,12 +199,15 @@ exports.parse = function (opts, code, callback) {
     if (!err._6to5) {
       err._6to5 = true;
       err.message = opts.filename + ": " + err.message;
-      Error.captureStackTrace(err);
+
       if (err.lineNumber) {
         var frame = exports.codeFrame(code, err.lineNumber, err.column);
-        err.message = err.message + frame;
+        var err2 = new SyntaxError(err.message + frame);
+        err2._6to5 = true;
+        throw err2;
       }
     }
+
     throw err;
   }
 };