diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 852d7474b3ee6c7d75bc21f71f1405670ddd12a0..387dcfd93461603ad7e4e2554c4e3c1891431f35 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -12,7 +12,7 @@ variables:
 check-no-old-frama-c:
   stage: git-update
   script:
-   - ! git merge-base --is-ancestor a1e186c68a6418a53b3dc06237f49e8dcbf75f4a HEAD
+   - (! git merge-base --is-ancestor a1e186c68a6418a53b3dc06237f49e8dcbf75f4a HEAD)
    - git merge-base --is-ancestor a35d2118fe6999dddce9e1847eff626fae9cc37c HEAD
   tags:
    - nix