make html doesn't update toctree sidebars of previously compiled pages, is it a bug?

[studyingegret]

When index.rst has toctree that changes from

.. toctree::
   it
   that

to

.. toctree::
   it
   that
   this

If I run make html before the change, I can see the sidebars of index, it and that having it and that. If I run make html again after the change, only index and this's toctree sidebar has the newly added this. it and that's don't. Is it a bug?