diff --git a/@xen-orchestra/backups/RemoteAdapter.js b/@xen-orchestra/backups/RemoteAdapter.js
index 631f8a2b2..4de36ae88 100644
--- a/@xen-orchestra/backups/RemoteAdapter.js
+++ b/@xen-orchestra/backups/RemoteAdapter.js
@@ -16,6 +16,7 @@ const { BACKUP_DIR } = require('./_getVmBackupDir')
 const { cleanVm } = require('./_cleanVm')
 const { getTmpDir } = require('./_getTmpDir')
 const { isMetadataFile, isVhdFile } = require('./_backupType')
+const { isValidXva } = require('./_isValidXva')
 const { listPartitions, LVM_PARTITION_TYPE } = require('./_listPartitions')
 const { lvs, pvs } = require('./_lvm')
 
@@ -551,8 +552,11 @@ class RemoteAdapter {
   }
 }
 
-RemoteAdapter.prototype.cleanVm = function (vmDir) {
-  return Disposable.use(this._handler.lock(vmDir), () => cleanVm.apply(this, arguments))
-}
+Object.assign(RemoteAdapter.prototype, {
+  cleanVm(vmDir) {
+    return Disposable.use(this._handler.lock(vmDir), () => cleanVm.apply(this, arguments))
+  },
+  isValidXva,
+})
 
 exports.RemoteAdapter = RemoteAdapter
diff --git a/@xen-orchestra/backups/_cleanVm.js b/@xen-orchestra/backups/_cleanVm.js
index 085a77407..73ddfb2fe 100644
--- a/@xen-orchestra/backups/_cleanVm.js
+++ b/@xen-orchestra/backups/_cleanVm.js
@@ -5,7 +5,6 @@ const { default: Vhd, mergeVhd } = require('vhd-lib')
 const { dirname, resolve } = require('path')
 const { DISK_TYPE_DIFFERENCING } = require('vhd-lib/dist/_constants')
 const { isMetadataFile, isVhdFile, isXvaFile, isXvaSumFile } = require('./_backupType')
-const { isValidXva } = require('./isValidXva')
 
 // chain is an array of VHDs from child to parent
 //
@@ -184,7 +183,7 @@ exports.cleanVm = async function cleanVm(vmDir, { remove, merge, onLog = noop })
   await asyncMap(xvas, async path => {
     // check is not good enough to delete the file, the best we can do is report
     // it
-    if (!(await isValidXva(path))) {
+    if (!(await this.isValidXva(path))) {
       onLog(`the XVA with path ${path} is potentially broken`)
     }
   })
diff --git a/@xen-orchestra/backups/isValidXva.js b/@xen-orchestra/backups/_isValidXva.js
similarity index 70%
rename from @xen-orchestra/backups/isValidXva.js
rename to @xen-orchestra/backups/_isValidXva.js
index 2949a324f..e38fb4a29 100644
--- a/@xen-orchestra/backups/isValidXva.js
+++ b/@xen-orchestra/backups/_isValidXva.js
@@ -1,10 +1,10 @@
 const assert = require('assert')
-const fs = require('fs-extra')
 
-const isGzipFile = async fd => {
+const isGzipFile = async (handler, fd) => {
   // https://tools.ietf.org/html/rfc1952.html#page-5
   const magicNumber = Buffer.allocUnsafe(2)
-  assert.strictEqual((await fs.read(fd, magicNumber, 0, magicNumber.length, 0)).bytesRead, magicNumber.length)
+
+  assert.strictEqual((await handler.read(fd, magicNumber, 0)).bytesRead, magicNumber.length)
   return magicNumber[0] === 31 && magicNumber[1] === 139
 }
 
@@ -21,32 +21,33 @@ const isGzipFile = async fd => {
 // /^Ref:\d+/\d+\.checksum$/ and then validating the tar structure from it
 //
 // https://github.com/npm/node-tar/issues/234#issuecomment-538190295
-const isValidTar = async (size, fd) => {
+const isValidTar = async (handler, size, fd) => {
   if (size <= 1024 || size % 512 !== 0) {
     return false
   }
 
   const buf = Buffer.allocUnsafe(1024)
-  assert.strictEqual((await fs.read(fd, buf, 0, buf.length, size - buf.length)).bytesRead, buf.length)
+  assert.strictEqual((await handler.read(fd, buf, size - buf.length)).bytesRead, buf.length)
   return buf.every(_ => _ === 0)
 }
 
 // TODO: find an heuristic for compressed files
-const isValidXva = async path => {
+async function isValidXva(path) {
+  const handler = this._handler
   try {
-    const fd = await fs.open(path, 'r')
+    const fd = await handler.openFile(path, 'r')
     try {
-      const { size } = await fs.fstat(fd)
+      const size = await handler.getSize(fd)
       if (size < 20) {
         // neither a valid gzip not tar
         return false
       }
 
-      return (await isGzipFile(fd))
+      return (await isGzipFile(handler, fd))
         ? true // gzip files cannot be validated at this time
-        : await isValidTar(size, fd)
+        : await isValidTar(handler, size, fd)
     } finally {
-      fs.close(fd).catch(noop)
+      handler.closeFile(fd).catch(noop)
     }
   } catch (error) {
     // never throw, log and report as valid to avoid side effects
diff --git a/@xen-orchestra/backups/writers/_FullBackupWriter.js b/@xen-orchestra/backups/writers/_FullBackupWriter.js
index 6e8c32512..055704492 100644
--- a/@xen-orchestra/backups/writers/_FullBackupWriter.js
+++ b/@xen-orchestra/backups/writers/_FullBackupWriter.js
@@ -1,7 +1,6 @@
 const { formatFilenameDate } = require('../_filenameDate')
 const { getOldEntries } = require('../_getOldEntries')
 const { getVmBackupDir } = require('../_getVmBackupDir')
-const { isValidXva } = require('../isValidXva')
 const { Task } = require('../Task')
 
 const { MixinBackupWriter } = require('./_MixinBackupWriter')
@@ -68,11 +67,7 @@ exports.FullBackupWriter = class FullBackupWriter extends MixinBackupWriter(Abst
 
     await Task.run({ name: 'transfer' }, async () => {
       await adapter.outputStream(dataFilename, stream, {
-        validator: tmpPath => {
-          if (handler._getFilePath !== undefined) {
-            return isValidXva(handler._getFilePath('/' + tmpPath))
-          }
-        },
+        validator: tmpPath => adapter.isValidXva(tmpPath),
       })
       return { size: sizeContainer.size }
     })