diff --git a/src/doc/README_SETUP.md b/src/doc/README_SETUP.md
index 952a8c94a7dfa24110f320f5dd32b0ad2ac1df01..5f5161d0d672ff3ad14db5c5b49f5c65550b06d7 100644
--- a/src/doc/README_SETUP.md
+++ b/src/doc/README_SETUP.md
@@ -17,6 +17,7 @@ Build documentation in `src/doc` with `make html`.
 - `sphinx`
 - `sphinx-autoapi`
 - `recommonmark`
+- `sphinx-rtd-theme`
 
 ### How to contribute ###