diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c722f3c334d412eb2796cff2d46e4e01f063e18d..c87df155590c022a2a4ecb86620ba59c211a63d5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -25,6 +25,7 @@ tests:
         - apt update
         - apt install -y libgl1-mesa-glx xvfb
         - pip install tox
+        - apt install -y graphviz
         - xvfb-run -s "-screen 0 800x600x24" tox
 
 build_and_deploy_docs: