diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index 894f7ca869..7d15509388 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -212,6 +212,7 @@ File.prototype.addHelper = function (name) {
 
   var runtime = this.get("runtimeIdentifier");
   if (runtime) {
+    name = t.identifier(t.toIdentifier(name));
     return t.memberExpression(runtime, name);
   } else {
     var ref = util.template(name);