diff --git a/docker/backend/Dockerfile b/docker/backend/Dockerfile
index 79e3f46f3..2fb91d587 100644
--- a/docker/backend/Dockerfile
+++ b/docker/backend/Dockerfile
@@ -25,7 +25,8 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 --mount=type=cache,target=/var/lib/apt,sharing=locked \
 apt-get -y update && apt-get -y install texlive-latex-recommended texlive-luatex texlive-plain-generic texlive-lang-german texlive-lang-english
 
-ENV PROJECT_DIR=/fradrive
+ARG PROJECT_DIR=/fradrive
+ENV PROJECT_DIR=${PROJECT_DIR}
 RUN mkdir -p "${PROJECT_DIR}"; chmod -R 7777 "${PROJECT_DIR}"
 WORKDIR ${PROJECT_DIR}
 ENV HOME=${PROJECT_DIR}