diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f5a14f0b59ce2355c2a9ca7f46c0860aeb83f198..667cbea2e0598d221c23d67e05211b86b36cb637 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -442,7 +442,7 @@ sphinx-documentation:
   stage: documentation
   before_script:
     - sudo apt-get update
-    - sudo apt-get install -y git
+    - sudo apt-get install -y git graphviz
   script:
     - cd tangostationcontrol
     - tox -e docs