diff --git a/pyproject.toml b/pyproject.toml
index b938826..eda0b38 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,7 +25,7 @@ classifiers = [
 dynamic = ["version", "description"]
 dependencies = [
   "pydata-sphinx-theme>=0.12.0,<0.13",
-  "sphinx>=5,<6",
+  "sphinx>=4,<6",
   "docutils==0.17.1",
 ]