diff --git a/.readthedocs.yml b/.readthedocs.yml
index c51a73699..5c95d6c8d 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -9,6 +9,7 @@ build:
   apt_packages:
     - libhdf5-dev
     - libnetcdf-dev
+    - graphviz
   os: ubuntu-22.04
   tools:
     python: "3.7"