diff --git a/.readthedocs.yml b/.readthedocs.yml
index 35eff5de..b5dc5eba 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -8,8 +8,11 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.11"
+  apt_packages:
+    - graphviz
 
 python:
   install:
   - requirements: doc/requirements.txt
   system_packages: false
+  apt_packages: