diff --git a/simple_backup/simple_backup.py b/simple_backup/simple_backup.py
index ebde737..ff28966 100755
--- a/simple_backup/simple_backup.py
+++ b/simple_backup/simple_backup.py
@@ -630,7 +630,7 @@ class Backup:
         # rsync splits the -e command itself, so quote the parts that may contain spaces
         if self.ssh_keyfile is not None:
             ssh = f'ssh -i {shlex.quote(self.ssh_keyfile)} -o StrictHostKeyChecking=accept-new'
-        elif self._password_auth and which('sshpass'):
+        elif self._password_auth and self.ssh_user is not None and which('sshpass'):
             ssh = f'sshpass -e ssh -l {shlex.quote(self.ssh_user)} -o StrictHostKeyChecking=accept-new'
         else:
             ssh = 'ssh -o StrictHostKeyChecking=accept-new'