diff --git a/index.js b/index.js
index e52dc37..99d520e 100644
--- a/index.js
+++ b/index.js
@@ -958,7 +958,7 @@ Queue.prototype.schedule = function (when, job, done) {
     function saveUniqueJob(job, next) {
       // if a unique name is specified, save it with the job details
       if (job.data && job.data.unique) {
-        const jobDataKey = this._getJobDataKey(job.data.unique);
+        let jobDataKey = this._getJobDataKey(job.data.unique);
         this._saveJobData(jobDataKey, job, function (error) {
           next(error, job);
         });