diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 9948a10ec07457dae0a05241c10947aeff6fe737..24124fc8a01456cb9cd10eddee0070db77b3f82e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -13,6 +13,7 @@ stages:
   - unit-tests
   - integration-tests
   - packaging
+# See docker-compose/README.md for docker image behavior and explanation
 .base_docker_images:
   stage: images
   image: docker:latest