diff --git a/src/backupformat/rsync.js b/src/backupformat/rsync.js
index d802eeb27..d285b700a 100644
--- a/src/backupformat/rsync.js
+++ b/src/backupformat/rsync.js
@@ -78,17 +78,16 @@ async function addFile(sourceFile, encryption, uploader, progressCallback) {
     await uploader.finish();
 }
 
-function sync(backupConfig, remotePath, dataLayout, progressCallback, callback) {
+async function sync(backupConfig, remotePath, dataLayout, progressCallback) {
     assert.strictEqual(typeof backupConfig, 'object');
     assert.strictEqual(typeof remotePath, 'string');
     assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
     assert.strictEqual(typeof progressCallback, 'function');
-    assert.strictEqual(typeof callback, 'function');
 
     // the number here has to take into account the s3.upload partSize (which is 10MB). So 20=200MB
     const concurrency = backupConfig.limits?.syncConcurrency || (backupConfig.provider === 's3' ? 20 : 10);
 
-    syncer.sync(dataLayout, async function processTask(task) {
+    await syncer.sync(dataLayout, async function processTask(task) {
         debug('sync: processing task: %j', task);
         // the empty task.path is special to signify the directory
         const destPath = task.path && backupConfig.encryptedFilenames ? hush.encryptFilePath(task.path, backupConfig.encryption) : task.path;
@@ -109,11 +108,7 @@ function sync(backupConfig, remotePath, dataLayout, progressCallback, callback)
                 await addFile(dataLayout.toLocalPath('./' + task.path), backupConfig.encryption, uploader, progressCallback);
             });
         }
-    }, concurrency, function (error) {
-        if (error) return callback(new BoxError(BoxError.EXTERNAL_ERROR, error.message));
-
-        callback();
-    });
+    }, concurrency);
 }
 
 // this is not part of 'snapshotting' because we need root access to traverse
@@ -263,8 +258,6 @@ async function upload(backupConfig, remotePath, dataLayout, progressCallback) {
     assert.strictEqual(typeof dataLayout, 'object');
     assert.strictEqual(typeof progressCallback, 'function');
 
-    const syncAsync = util.promisify(sync);
-
     await saveFsMetadata(dataLayout, `${dataLayout.localRoot()}/fsmetadata.json`);
-    await syncAsync(backupConfig, remotePath, dataLayout, progressCallback);
+    await sync(backupConfig, remotePath, dataLayout, progressCallback);
 }
diff --git a/src/syncer.js b/src/syncer.js
index 1d7f78b6f..40cac5ab9 100644
--- a/src/syncer.js
+++ b/src/syncer.js
@@ -8,10 +8,11 @@ const assert = require('assert'),
     fs = require('fs'),
     path = require('path'),
     paths = require('./paths.js'),
-    safe = require('safetydance');
+    safe = require('safetydance'),
+    util = require('util');
 
 exports = module.exports = {
-    sync
+    sync: util.promisify(sync)
 };
 
 function readCache(cacheFile) {