diff --git a/dnf/automatic/main.py b/dnf/automatic/main.py
index e9273c5dd6..118bb20474 100644
--- a/dnf/automatic/main.py
+++ b/dnf/automatic/main.py
@@ -379,7 +379,7 @@ def main(args):
                (conf.commands.reboot == 'when-needed' and base.reboot_needed())):
                 exit_code = os.waitstatus_to_exitcode(os.system(conf.commands.reboot_command))
                 if exit_code != 0:
-                    raise dnf.exceptions.Error('reboot command returned nonzero exit code: %d', exit_code)
+                    raise dnf.exceptions.Error('reboot command returned nonzero exit code: %d' % exit_code)
     except Exception as exc:
         logger.error(_('Error: %s'), ucd(exc))
         if conf is not None and conf.emitters.send_error_messages and emitters is not None: