diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3a59f6307f0a8fc5895843db3a22600153bbe28c..d9b998048ce10497d1f01fea4429c2952bc06d46 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -9,6 +9,7 @@ variables:
   PERL5LIB: "$EXTLIB/lib/perl5/:lib"
   # Make sure to use only codenames that are supported by SLUB's Debian repo server!
   DEBIAN_DEFAULT_RELEASE: "bookworm"
+  DEBIAN_RELEASE: "${DEBIAN_DEFAULT_RELEASE}"
   DEBIAN_RELEASES: "${DEBIAN_DEFAULT_RELEASE}"
   IMAGE_TARGET: "${HARBOR_HOST}/${HARBOR_PROJECT}/${DEBIAN_DEFAULT_RELEASE}_${HARBOR_PROJECT}"
   FF_USE_FASTZIP: "true"
@@ -56,6 +57,7 @@ build-env-job:       # This job runs in the build stage, which runs first.
       --dockerfile "${CI_PROJECT_DIR}/gitlab-ci/Dockerfile"
       --destination "${IMAGE_TARGET}:latest"
       --build-arg "GITDIR=${CI_PROJECT_DIR}"
+      --build-arg "DEBIAN_RELEASE"
       --cache=true
       --cache-repo=${CI_REGISTRY_IMAGE}
       --cache-copy-layers=true