diff --git a/python/samba/netcmd/domain_backup.py b/python/samba/netcmd/domain_backup.py
index 9eae6d3c3cfe..ceba98039b70 100644
--- a/python/samba/netcmd/domain_backup.py
+++ b/python/samba/netcmd/domain_backup.py
@@ -1156,6 +1156,7 @@ def run(self, sambaopts=None, targetdir=None):
         # Backup secrets, sam.ldb and their downstream files
         self.backup_secrets(paths.private_dir, lp, logger)
         self.backup_smb_dbs(paths.private_dir, samdb, lp, logger)
+        samdb = None
 
         # Open the new backed up samdb, flag it as backed up, and write
         # the next SID so the restore tool can add objects.