diff --git a/src/sphinx_subfigure/main.py b/src/sphinx_subfigure/main.py
index 377449c..c47d3c5 100644
--- a/src/sphinx_subfigure/main.py
+++ b/src/sphinx_subfigure/main.py
@@ -2,22 +2,33 @@
 
 import math
 import string
+from typing import TYPE_CHECKING
 
 from docutils import nodes
 from docutils.parsers.rst import directives
 from sphinx.application import Sphinx
 from sphinx.util.docutils import SphinxDirective
 
+from . import __version__
 from .tr_html import setup_html
 from .tr_latex import setup_latex
 
+if TYPE_CHECKING:
+    from typing import Any
 
-def setup(app: Sphinx) -> None:
+
+def setup(app: Sphinx) -> dict[str, Any]:
     """Setup the extension."""
     app.add_directive("subfigure", SubfigureDirective)
     setup_html(app)
     setup_latex(app)
 
+    return {
+        "version": __version__,
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }
+
 
 class SubfigureDirective(SphinxDirective):
     """A sphinx directive to create sub-figures."""
diff --git a/tox.ini b/tox.ini
index b932ec1..bb80469 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,11 +16,11 @@ description = Build the documentation
 extras = docs
 setenv =
     BUILDER = {env:BUILDER:html}
-whitelist_externals =
+allowlist_externals =
     echo
     rm
 commands_pre = rm -rf docs/_build/{env:BUILDER}
-commands = sphinx-build -nW --keep-going -b {env:BUILDER} {posargs} docs/ docs/_build/{env:BUILDER}
+commands = sphinx-build -nW --keep-going -b {env:BUILDER} -j auto {posargs} docs/ docs/_build/{env:BUILDER}
 commands_post = echo "open file://{toxinidir}/docs/_build/html/index.html"
 
 [flake8]