diff --git a/src/middlewared/middlewared/plugins/cloud_backup/sync.py b/src/middlewared/middlewared/plugins/cloud_backup/sync.py
index 46d02cab27ad2..0f36793c082a8 100644
--- a/src/middlewared/middlewared/plugins/cloud_backup/sync.py
+++ b/src/middlewared/middlewared/plugins/cloud_backup/sync.py
@@ -146,7 +146,7 @@ async def _sync(self, cloud_backup, options, job):
             restic_config = get_restic_config(cloud_backup)
             await run_restic(
                 job,
-                restic_config.cmd + ["forget", "--keep-last", str(cloud_backup["keep_last"])],
+                restic_config.cmd + ["forget", "--keep-last", str(cloud_backup["keep_last"]), "--prune"],
                 restic_config.env,
             )