diff --git a/lib/passport-cas.js b/lib/passport-cas.js
index d167425..4f096e7 100644
--- a/lib/passport-cas.js
+++ b/lib/passport-cas.js
@@ -119,9 +119,9 @@ CasStrategy.prototype.authenticate = function (req, options) {
   if (!req._passport) { return this.error(new Error('passport.initialize() middleware not in use')); }
   options = options || {};
 
-  const self = this;
-  const reqURL = url.parse(req.originalUrl || req.url, true);
-  let service;
+  var self = this;
+  var reqURL = url.parse(req.originalUrl || req.url, true);
+  var service;
 
   // The provided `verify` callback will call this on completion
   function verified(err, user, info) {