diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a044e8ba50f41f09e9c89062f3f0ed18f1d74d15..118bc741e0f8b4be03fe59e1f98485058852fe71 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -27,12 +27,16 @@ tests-on-llvm-10:
   stage: tests
   script:
    - nix/frama-ci.sh build -A frama-clang.on-llvm10.tests
+  tags:
+   - nix
   when: manual
 
 tests-on-llvm-11:
   stage: tests
   script:
    - nix/frama-ci.sh build -A frama-clang.on-llvm11.tests
+  tags:
+   - nix
   when: manual
 
 tests-on-llvm-13: