diff --git a/pyproject.toml b/pyproject.toml
index 19e7eda..a4a19f5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -48,8 +48,8 @@ wavinfo = 'wavinfo.__main__:main'
 [tool.poetry.dependencies]
 python = "^3.8"
 lxml = "~= 5.3.0"
-sphinx_rtd_theme = {version= '>= 1.1.1', optional=true}
-sphinx = {version= '>= 5.3.0', optional=true}
+sphinx_rtd_theme = {version= '>= 1.1.1', optional=true, extras=['doc']}
+sphinx = {version= '>= 5.3.0', optional=true, extras=['doc']}
 
 [tool.pyright]
 typeCheckingMode = "basic"