diff --git a/joy/gui/world.py b/joy/gui/world.py
index 9682064..83d2fa6 100644
--- a/joy/gui/world.py
+++ b/joy/gui/world.py
@@ -141,7 +141,7 @@ class StackDisplayWorld(World):
       os.fsync(f.fileno())
     self.repo.stage([self.relative_STACK_FN])
     commit_id = self.repo.do_commit(
-      'message',
+      b'auto-save',
       committer=b'Simon Forman <forman.simon@gmail.com>',
       )
     _log.info('commit %s', commit_id)