diff --git a/builder/build-tarball b/builder/build-tarball
index 66b94b5..5be8dd8 100755
--- a/builder/build-tarball
+++ b/builder/build-tarball
@@ -19,9 +19,11 @@ move_libjpeg_turbo_to_os_specific_dir() {
     $PWD/builder/build/${os_codename}/
 }
 
+echo "GITLAB_SHARED_DIND_DIR= ${GITLAB_SHARED_DIND_DIR}"
 shared_with_docker_dir=${GITLAB_SHARED_DIND_DIR:-/tmp}
-# some gitlab runners may not have a shared dind configured
-if [ ! -w "$GITLAB_SHARED_DIND_DIR" ]; then GITLAB_SHARED_DIND_DIR="/tmp"; fi
+# fall back to /tmp if not writable
+if [ ! -w "$GITLAB_SHARED_DIND_DIR" ]; then shared_with_docker_dir="/tmp"; fi
+echo "SHARED_WITH_DOCKER_DIR= ${shared_with_docker_dir}"
 
 cd "$(dirname "$0")/.."
 . builder/os_ver_cli.sh