diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b794a61c233bb7528698c4d43c5718c99cdf192f..07ee4734182c2117315b3c48c434e5d351c855b2 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -279,6 +279,7 @@ ocaml-versions-nightly:
   stage: compatibility
   image: 'ocaml/opam:ubuntu-20.04-ocaml-$OCAML'
   script:
+    - sudo apt update
     - opam pin . -n
     - opam depext frama-c --with-test
     - opam install --jobs 2 frama-c --with-test