diff --git a/pyproject.toml b/pyproject.toml
index 4bbc1ef..5031365 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,6 +75,7 @@ pre-commit = {version = "*", optional = true}
 pylint = {version = "*", optional = true}
 pytest = {version = "*", optional = true}
 ruff = {version = "*", optional = true}
+sphinx = {version = "*", optional = true}
 tox = {version = "*", optional = true}
 
 [tool.poetry.extras]