diff --git a/docs/tutorials/tictactoe.rst b/docs/tutorials/tictactoe.rst
index a6f5527e5..c8eec3ce6 100644
--- a/docs/tutorials/tictactoe.rst
+++ b/docs/tutorials/tictactoe.rst
@@ -1,5 +1,5 @@
 RL against random policy opponent with PettingZoo
-==============
+=================================================
 
 Tianshou is compatible with `PettingZoo` environments for multi-agent RL, although does not directly provide facilities for multi-agent RL. Here are some helpful tutorial links: