diff --git a/CHANGELOG.unreleased.md b/CHANGELOG.unreleased.md
index 4e662ef89fe..f710c012bf8 100644
--- a/CHANGELOG.unreleased.md
+++ b/CHANGELOG.unreleased.md
@@ -68,6 +68,7 @@
 - [REST API] Expose `/rest/v0/pbds` and `/rest/v0/pbds/:id` (PR [#9106](https://github.com/vatesfr/xen-orchestra/pull/9106))
 
 - [Plugins/SAML] Add two fields to configure assertions and responses signatures (PR [#9093](https://github.com/vatesfr/xen-orchestra/pull/9093))
+- [Backups] Add `Merge backups synchronously` to mirror backup (PR [#9118](https://github.com/vatesfr/xen-orchestra/pull/9118))
 
 - **XO 6:**
   - [Collections] Implement virtual lists for tasks and alarms to improve performance (PR [#9077](https://github.com/vatesfr/xen-orchestra/pull/9077))
@@ -107,6 +108,6 @@
 - @xen-orchestra/web-core minor
 - xo-server minor
 - xo-server-auth-saml minor
-- xo-web patch
+- xo-web minor
 
 <!--packages-end-->
diff --git a/packages/xo-web/src/xo-app/backup/new/mirror/index.js b/packages/xo-web/src/xo-app/backup/new/mirror/index.js
index c2b4ea3d4fa..1dc1c1c5a36 100644
--- a/packages/xo-web/src/xo-app/backup/new/mirror/index.js
+++ b/packages/xo-web/src/xo-app/backup/new/mirror/index.js
@@ -237,6 +237,8 @@ const NewMirrorBackup = decorate([
       onChangeVmBackups: (_, vmBackups) => () => ({
         vmsToMirror: vmBackups.map(({ value: vmUuid }) => vmUuid),
       }),
+      setMergeBackupsSynchronously: ({ setAdvancedSettings }, mergeBackupsSynchronously) =>
+        setAdvancedSettings({ mergeBackupsSynchronously }),
     },
     computed: {
       vmBackupOptions: async state => {
@@ -317,6 +319,7 @@ const NewMirrorBackup = decorate([
       backupReportTpl = 'mjml',
       hideSuccessfulItems,
       nRetriesVmBackupFailures = 0,
+      mergeBackupsSynchronously,
     } = state.advancedSettings
     return (
       <form id={state.formId}>
@@ -458,6 +461,21 @@ const NewMirrorBackup = decorate([
                           onChange={effects.setHideSuccessfulItems}
                         />
                       </FormGroup>
+                      <FormGroup>
+                        <label htmlFor={state.inputMergeBackupsSynchronously}>
+                          <strong>{_('mergeBackupsSynchronously')}</strong>
+                        </label>{' '}
+                        <Tooltip content={_('mergeBackupsSynchronouslyTooltip')}>
+                          <Icon icon='info' />
+                        </Tooltip>
+                        <Toggle
+                          className='pull-right'
+                          id={state.inputMergeBackupsSynchronously}
+                          name='mergeBackupsSynchronously'
+                          value={mergeBackupsSynchronously}
+                          onChange={effects.setMergeBackupsSynchronously}
+                        />
+                      </FormGroup>
                     </div>
                   )}
                 </CardBlock>