diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a68bd7abb73fa46a325d150bd125a9b75a341844..ca3289fe7871aed9a982048e03f275ec24c97537 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -48,7 +48,7 @@ header-check:
   stage: build
   script:
     - ls -la
-    - nix-shell nix/pkgs.nix -A ocaml-ng.ocamlPackages_4_12.frama-c-checkers-shell
+    - nix-shell nix/pkgs.nix -A ocaml-ng.ocamlPackages_$OCAML.frama-c-checkers-shell
         --run 'FRAMAC_HDRCK="" make -f share/Makefile.headers check-headers'
   tags:
     - nix