diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fd07745..406da9a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -82,11 +82,12 @@ pages:
 
 
 docker-build:
-  # Use the official docker image.
   image: docker:latest
   stage: build
   services:
     - docker:dind
+  variables:
+    GIT_SUBMODULE_STRATEGY: recursive
   before_script:
     - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
   # Default branch leaves tag empty (= latest tag)