"let" not supported?

Author: noel-schenk

lib/consolidate.js

@@ -1774,8 +1774,8 @@ exports.twing.render = function(str, options, cb) {
   return promisify(cb, function(cb) {
     var engine = requires.twing || (requires.twing = require('twing'));
     try {
-      let rendTmpl = new engine.TwingEnvironment(new engine.TwingLoaderNull()).createTemplate(str).render(options);
-      let tmpl = cache(options) || cache(options, rendTmpl);
+      var rendTmpl = new engine.TwingEnvironment(new engine.TwingLoaderNull()).createTemplate(str).render(options);
+      var tmpl = cache(options) || cache(options, rendTmpl);
       cb(null, tmpl);
     } catch (err) {
       cb(err);