diff --git a/src/backupformat/tgz.js b/src/backupformat/tgz.js
index cfa5873e4..cf4c41272 100644
--- a/src/backupformat/tgz.js
+++ b/src/backupformat/tgz.js
@@ -1,11 +1,5 @@
 'use strict';
 
-exports = module.exports = {
-    getBackupFilePath,
-    download,
-    upload
-};
-
 const assert = require('assert'),
     BoxError = require('../boxerror.js'),
     DataLayout = require('../datalayout.js'),
@@ -272,3 +266,12 @@ async function upload(backupConfig, remotePath, dataLayout, progressCallback) {
         await tarPack(dataLayout, backupConfig.encryption, uploader, progressCallback);
     });
 }
+
+exports = module.exports = {
+    getBackupFilePath,
+    download,
+    upload,
+
+    // exported for testing
+    _EnsureFileSizeStream: EnsureFileSizeStream
+};
diff --git a/src/hush.js b/src/hush.js
index c86ff5046..63b3b97ff 100644
--- a/src/hush.js
+++ b/src/hush.js
@@ -4,8 +4,6 @@ const assert = require('assert'),
     BoxError = require('./boxerror.js'),
     crypto = require('crypto'),
     debug = require('debug')('box:hush'),
-    fs = require('fs'),
-    ProgressStream = require('./progress-stream.js'),
     TransformStream = require('stream').Transform;
 
 class EncryptStream extends TransformStream {
diff --git a/src/test/backupformat-test.js b/src/test/backupformat-test.js
index 1aceb052b..b258ed484 100644
--- a/src/test/backupformat-test.js
+++ b/src/test/backupformat-test.js
@@ -8,11 +8,14 @@
 
 const common = require('./common.js'),
     DataLayout = require('../datalayout.js'),
+    EnsureFileSizeStream = require('../backupformat/tgz.js')._EnsureFileSizeStream,
     expect = require('expect.js'),
     fs = require('fs'),
     os = require('os'),
     path = require('path'),
-    rsync = require('../backupformat/rsync.js');
+    rsync = require('../backupformat/rsync.js'),
+    safe = require('safetydance'),
+    stream = require('node:stream/promises');
 
 describe('backuptask', function () {
     const { setup, cleanup, createTree } = common;
@@ -20,6 +23,47 @@ describe('backuptask', function () {
     before(setup);
     after(cleanup);
 
+    describe('EnsureFileSizeStream', function () {
+        const name = 'eberswalde.txt';
+        const data = Buffer.from('This file has 22 bytes');
+        before(function () {
+            fs.writeFileSync(`/tmp/${name}`, data);
+        });
+        after(function () {
+            fs.rmSync(`/tmp/${name}`);
+        });
+
+        it('correct size', async function () {
+            const efs = new EnsureFileSizeStream({ name, size: 22 });
+            const ins = fs.createReadStream(`/tmp/${name}`);
+            const outs = fs.createWriteStream('/tmp/out.txt');
+            const [error] = await safe(stream.pipeline(ins, efs, outs));
+            expect(error).to.be(null);
+            const out = fs.readFileSync('/tmp/out.txt');
+            expect(out).to.eql(data);
+        });
+
+        it('overflow', async function () {
+            const efs = new EnsureFileSizeStream({ name, size: 20 });
+            const ins = fs.createReadStream(`/tmp/${name}`);
+            const outs = fs.createWriteStream('/tmp/out.txt');
+            const [error] = await safe(stream.pipeline(ins, efs, outs));
+            expect(error).to.be(null);
+            const out = fs.readFileSync('/tmp/out.txt');
+            expect(out).to.eql(data.subarray(0, 20));
+        });
+
+        it('underflow', async function () {
+            const efs = new EnsureFileSizeStream({ name, size: 30 });
+            const ins = fs.createReadStream(`/tmp/${name}`);
+            const outs = fs.createWriteStream('/tmp/out.txt');
+            const [error] = await safe(stream.pipeline(ins, efs, outs));
+            expect(error).to.be(null);
+            const out = fs.readFileSync('/tmp/out.txt');
+            expect(out).to.eql(Buffer.concat([data, Buffer.alloc(8)]));
+        });
+    });
+
     describe('fs meta data', function () {
         let tmpdir;
         before(function () {