diff --git a/docker/backend/Dockerfile b/docker/backend/Dockerfile
index a17020fb5..098bfdfa5 100644
--- a/docker/backend/Dockerfile
+++ b/docker/backend/Dockerfile
@@ -6,16 +6,19 @@ RUN apt-get -y update && apt-get -y install llvm
 
 ENV LANG=en_US.UTF-8
 
+# locally these two should be identical, so that compilation results are written out into the file dir.
+# in CI-pipelines these two should be different, so that the container caches the compilation results.
+ARG MOUNT_DIR=/mnt/fradrive
 ARG PROJECT_DIR=/fradrive
 RUN mkdir -p ${PROJECT_DIR}
-RUN cp -r /tmp/${PROJECT_DIR}/* ${PROJECT_DIR}
+RUN if [ "${PROJECT_DIR}" != "${MOUNT_DIR}" ] ; then cp -r ${MOUNT_DIR}/* ${PROJECT_DIR} ; fi
 WORKDIR ${PROJECT_DIR}
 ENV HOME=${PROJECT_DIR}
 
 RUN mkdir -p /.stack
 ENV STACK_ROOT=/.stack
 
-RUN make backend-dependencies STACK_ROOT=${STACK_ROOT}
+RUN make .stack STACK_ROOT=${STACK_ROOT} IN_CONTAINER=true
 
 ENV FRADRIVE_MAKE_TARGET=backend-build
-ENTRYPOINT make -- ${FRADRIVE_MAKE_TARGET} STACK_ROOT=${STACK_ROOT}
\ No newline at end of file
+ENTRYPOINT make -- ${FRADRIVE_MAKE_TARGET} STACK_ROOT=${STACK_ROOT} IN_CONTAINER=true
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