diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 3663f37..6e6fa84 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -13,6 +13,8 @@
   os: ubuntu-22.04 # Ubuntu Jammy LTS
   tools:
     python: "3.10"
+  apt_packages:
+    - plantuml
 
 python:
   install: