diff --git a/lib/main.js b/lib/main.js
index 8a3e510e..91251ba7 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -615,21 +615,26 @@ Lambda.prototype._updateEventSources = function (lambda, functionName, existingE
   })
 }
 
-Lambda.prototype._updateScheduleEvents = function (scheduleEvents, functionArn, scheduleList, cb) {
+Lambda.prototype._updateScheduleEvents = (scheduleEvents, functionArn, scheduleList, cb) => {
   if (scheduleList == null) {
     return cb(null, [])
   }
-  return async.series(scheduleList.map(function (schedule) {
-    return function (_cb) {
-      const params = Object.assign(schedule, { FunctionArn: functionArn })
-      scheduleEvents.add(params).then(function (data) {
-        _cb(null, params)
-      }).catch(function (err) {
-        _cb(err)
-      })
-    }
-  }), function (err, results) {
-    cb(err, results)
+
+  const paramsList = scheduleList.map((schedule) =>
+    Object.assign(schedule, { FunctionArn: functionArn }))
+
+  // series
+  paramsList.map((params) => {
+    return scheduleEvents.add(params)
+  }).reduce((a, b) => {
+    return a.then(b)
+  }, Promise.resolve()).then(() => {
+    // Since `scheduleEvents.add(params)` returns only `{}` if it succeeds
+    // it is not very meaningful.
+    // Therefore, return the params used for execution
+    cb(null, paramsList)
+  }).catch((err) => {
+    cb(err)
   })
 }
 
diff --git a/test/main.js b/test/main.js
index 9d2ae9e5..83347fbe 100644
--- a/test/main.js
+++ b/test/main.js
@@ -807,7 +807,7 @@ describe('lib/main', function () {
         })
       }).then(function (actual) {
         const expected = {
-          err: undefined,
+          err: null,
           results: [Object.assign(
             eventSourcesJsonValue.ScheduleEvents[0],
             { FunctionArn: functionArn }