diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 2935765db91d138e46a803e4aaa83ba8b6cd1e98..a17158a2bfd860b971103467703e9dd33b3a0b8e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -138,6 +138,7 @@ pages:
   stage: deploy
   image: python:3.10
   script:
+    - apt-get install --yes optipng
     - pip install -r requirements_doc.txt
     - sphinx-build -b html docs_sphinx public
   artifacts: