diff --git a/.github/workflows/sphinx-build.yml b/.github/workflows/sphinx-build.yml
index c94fcc3b..2c50c3cc 100644
--- a/.github/workflows/sphinx-build.yml
+++ b/.github/workflows/sphinx-build.yml
@@ -21,7 +21,7 @@ jobs:
 
     - uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.12
 
     - name: Install Dependencies
       run: |
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 055b6355..6a67f190 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -16,10 +16,10 @@
 # import sys
 # sys.path.insert(0, os.path.abspath('.'))
 
-import pkg_resources
+from importlib.metadata import version
 
 
-__version__ = pkg_resources.get_distribution("optuna-integration").version
+__version__ = version("optuna-integration")
 
 # -- Project information -----------------------------------------------------
 
@@ -42,6 +42,7 @@
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
+    "notfound.extension",
     "sphinx.ext.autodoc",
     "sphinx.ext.autosummary",
     "sphinx.ext.doctest",
diff --git a/pyproject.toml b/pyproject.toml
index 96f0346e..f683bf7d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -56,6 +56,7 @@ document = [
     "scikit-learn>=0.24.2",
     "scipy>=1.9.2; python_version>='3.8'",
     "sphinx",
+    "sphinx-notfound-page",
     "sphinx_rtd_theme",
 ]
 allennlp = [