diff --git a/.readthedocs.yml b/.readthedocs.yml
index 153757d4..a25a2907 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -18,7 +18,8 @@ build:
   os: ubuntu-lts-latest
   tools:
     python: latest
-
+  apt_packages:
+    - graphviz
 
 # Optionally set the version of Python and requirements required to build your docs
 python: