diff --git a/docs/source/conf.py b/docs/source/conf.py
index 151ac8ce1..92275a283 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -29,6 +29,7 @@
     "sphinx.ext.autodoc",
     "sphinx.ext.autosummary",
     "sphinx.ext.intersphinx",
+    "sphinx_rtd_theme",
     # "sphinx_autodoc_typehints",
     # "sphinx.ext.mathjax",
     # "sphinx.ext.ifconfig",