diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fb64ae7f33c7664ff35b842fc8c9303cf5398dd9..8e53ff6691064eb0c79b3beefe055292886190ba 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -27,5 +27,11 @@ tests-on-llvm-10:
   stage: tests
   script:
    - nix/frama-ci.sh build -A frama-clang.on-llvm10.tests
+  when: manual
+
+tests-on-llvm-11:
+  stage: tests
+  script:
+   - nix/frama-ci.sh build -A frama-clang.on-llvm11.tests
   tags:
    - nix
diff --git a/nix/default.nix b/nix/default.nix
index 2c8fdf94fbf13ca256470e73f6f3fa08b581b07f..9ce8bc747584d13c31af827e11090ee3ffc21e76 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -30,3 +30,4 @@ let frama_clang_build =
 in
 (frama_clang_build { llvm_version="9"; })
 // { on-llvm10 = (frama_clang_build { llvm_version="10"; });}
+// { on-llvm11 = (frama_clang_build { llvm_version="11"; });}