diff --git a/setup.py b/setup.py
index 12a7ec7..2598182 100644
--- a/setup.py
+++ b/setup.py
@@ -31,6 +31,7 @@
     include_package_data=True,
     install_requires=[
         "sphinx-book-theme>=1.0.0",
+        "sphinx>=5.0",
     ],
     packages=find_packages(),
     entry_points={"sphinx.html_themes": ["sphinx_pythia_theme = sphinx_pythia_theme"]},