diff --git a/docs/source/conf.py b/docs/source/conf.py
index 5cf7b3d..5a54542 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -5,8 +5,6 @@
 
 import os
 import shutil
-# At the top.
-import sphinx_bootstrap_theme
 
 def copy_tutorials(app):
     src = os.path.abspath("../tutorials")
diff --git a/pyproject.toml b/pyproject.toml
index 15f873c..53b75b8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,8 +42,7 @@ optional-dependencies.docs = [
   "pre-commit",
   "pyproject-fmt",
   "sphinx",
-  "sphinx-rtd-theme",
-  "sphinx_bootstrap_theme",
+  "sphinx-book-theme",
 ]
 optional-dependencies.test = [ "coverage", "pytest" ]
 urls."Source" = "https://github.com/max-models/template-python"