diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 73dd15b..9f41c9d 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -12,6 +12,9 @@
 # Stages run in sequential order, but jobs within stages run in parallel.
 #
 # For more information, see: https://docs.gitlab.com/ee/ci/yaml/index.html#stages
+
+# Specify the docker image to use (only used if using docker runners)
+# See http://doc.gitlab.com/ee/ci/docker/using_docker_images.html
 default:
   image: gcc-cmake