diff --git a/mdsite/mdsite.py b/mdsite/mdsite.py
index 2f43d2a..4168917 100644
--- a/mdsite/mdsite.py
+++ b/mdsite/mdsite.py
@@ -9,7 +9,6 @@
 from datetime import date
 from importlib.metadata import version
 from pathlib import Path
-from platformdirs import site_config_dir
 
 import yaml
 from jinja2 import Template
diff --git a/pyproject.toml b/pyproject.toml
index a475caf..51624fd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,6 +27,12 @@ homepage = "https://iizukak.github.io/mdsite/"
 documentation = "https://github.com/iizukak/mdsite/blob/main/README.md"
 repository = "https://github.com/iizukak/mdsite"
 
+[tool]
+rye = { dev-dependencies = [
+    "black>=23.9.1",
+    "pytest>=7.4.2",
+] }
+
 [tool.setuptools]
 zip-safe = false
 include-package-data = true