diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 78cfb5695f9632e57138b7112a7af100a5b675ec..3428fbf5980527ff40ccb49db2b38da51133befc 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,4 +1,6 @@
 default:
+  # Guide the choice of an appropriate runner for all these jobs.
+  # https://docs.gitlab.com/ee/ci/runners/#runner-runs-only-tagged-jobs
   tags:
     - "nixos"
     - "shell"