diff --git a/packages/xo-server/src/api/test.js b/packages/xo-server/src/api/test.js
index ef9d8dd02..15b8e5d08 100644
--- a/packages/xo-server/src/api/test.js
+++ b/packages/xo-server/src/api/test.js
@@ -65,7 +65,11 @@ export async function copyVm ({ vm, sr }) {
     console.log('export delta VM...')
     const input = await srcXapi.exportDeltaVm(vm)
     console.log('import delta VM...')
-    await tgtXapi.deleteVm(await tgtXapi.importDeltaVm(input, { srId: sr }))
+    const { transferSize, vm: copyVm } = await tgtXapi.importDeltaVm(input, {
+      srId: sr,
+    })
+    console.log('transfered size:', transferSize)
+    await tgtXapi.deleteVm(copyVm)
   }
 }
 
diff --git a/packages/xo-server/src/api/vm.js b/packages/xo-server/src/api/vm.js
index ff403406f..2622e3205 100644
--- a/packages/xo-server/src/api/vm.js
+++ b/packages/xo-server/src/api/vm.js
@@ -777,7 +777,7 @@ export function importDeltaBackup ({ sr, remote, filePath, mapVdisSrs }) {
     remoteId: remote,
     filePath,
     mapVdisSrs: mapVdisSrsXapi,
-  })
+  }).then(_ => _.vm)
 }
 
 importDeltaBackup.params = {
diff --git a/packages/xo-server/src/xapi/index.js b/packages/xo-server/src/xapi/index.js
index 505b9cd07..2c2aa115e 100644
--- a/packages/xo-server/src/xapi/index.js
+++ b/packages/xo-server/src/xapi/index.js
@@ -943,8 +943,6 @@ export default class Xapi extends XapiBase {
         baseVdis[vbd.VDI] = vbd.$VDI
       })
 
-    const { streams } = delta
-
     // 1. Create the VMs.
     const vm = await this._getOrWaitObject(
       await this._createVmRecord({
@@ -1012,6 +1010,9 @@ export default class Xapi extends XapiBase {
       defaultNetwork = networksOnPoolMasterByDevice[pif.device] = pif.$network
     })
 
+    const { streams } = delta
+    let transferSize = 0
+
     await Promise.all([
       // Create VBDs.
       asyncMap(delta.vbds, vbd =>
@@ -1028,7 +1029,13 @@ export default class Xapi extends XapiBase {
           if (typeof stream === 'function') {
             stream = await stream()
           }
-          await this._importVdiContent(vdi, stream, VDI_FORMAT_VHD)
+          const sizeStream = stream
+            .pipe(createSizeStream())
+            .once('finish', () => {
+              transferSize += sizeStream.size
+            })
+          stream.task = sizeStream.task
+          await this._importVdiContent(vdi, sizeStream, VDI_FORMAT_VHD)
         }
       }),
 
@@ -1064,7 +1071,7 @@ export default class Xapi extends XapiBase {
       }),
     ])
 
-    return vm
+    return { transferSize, vm }
   }
 
   async _migrateVmWithStorageMotion (
diff --git a/packages/xo-server/src/xo-mixins/backups.js b/packages/xo-server/src/xo-mixins/backups.js
index 148098033..54c687397 100644
--- a/packages/xo-server/src/xo-mixins/backups.js
+++ b/packages/xo-server/src/xo-mixins/backups.js
@@ -429,8 +429,7 @@ export default class {
     })(srcVm.other_config[TAG_LAST_BASE_DELTA])
 
     // 2. Copy.
-    let size = 0
-    const dstVm = await (async () => {
+    const { transferSize, vm: dstVm } = await (async () => {
       const { cancel, token } = CancelToken.source()
       const delta = await srcXapi.exportDeltaVm(
         token,
@@ -452,17 +451,6 @@ export default class {
       delta.vm.other_config[TAG_EXPORT_TIME] = date
       delta.vm.tags = [...delta.vm.tags, 'Continuous Replication']
 
-      const { streams } = delta
-      forEach(delta.vdis, (vdi, key) => {
-        const id = `${key}.vhd`
-        const stream = streams[id]
-        const sizeStream = createSizeStream().once('finish', () => {
-          size += sizeStream.size
-        })
-        sizeStream.task = stream.task
-        streams[id] = stream.pipe(sizeStream)
-      })
-
       let toRemove = filter(
         targetXapi.objects.all,
         obj => obj.$type === 'vm' && obj.other_config[TAG_SOURCE_VM] === uuid
@@ -508,7 +496,7 @@ export default class {
       // 5. Return the identifier of the new XO VM object.
       id: xapiObjectToXo(dstVm).id,
       transferDuration: Date.now() - transferStart,
-      transferSize: size,
+      transferSize,
     }
   }
 
@@ -914,11 +902,11 @@ export default class {
       delta.vm.name_label += ` (${shortDate(datetime * 1e3)})`
       delta.vm.tags.push('restored from backup')
 
-      vm = await xapi.importDeltaVm(delta, {
+      vm = (await xapi.importDeltaVm(delta, {
         disableStartAfterImport: false,
         srId: sr !== undefined && sr._xapiId,
         mapVdisSrs,
-      })
+      })).vm
     } else {
       throw new Error(`Unsupported delta backup version: ${version}`)
     }