diff --git a/docs/requirements.txt b/docs/requirements.txt
index 8e64ef952..732f30a96 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -8,6 +8,9 @@ Jinja2<3.1
 # Support Markdown
 #recommonmark
 
+# Theme
+sphinx-rtd-theme
+
 #Handle references in bibtex format
 sphinxcontrib-bibtex