diff --git a/Dockerfile b/Dockerfile
index 001920c..4569f50 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,7 +7,8 @@
 
 FROM scratch as bootstrap
 # Unpack the stage3 archive (which is downloaded and verifed externally).
-ADD latest-stage3.tar.xz /
+ARG ROOTFS_FILENAME=""
+ADD ${ROOTFS_FILENAME} /
 # Set the profile.
 RUN eselect profile set "default/linux/amd64/17.1/no-multilib/systemd/merged-usr"
 # Replace /etc/portage/make.conf.
diff --git a/build-image.sh b/build-image.sh
index 7d8d636..c0a346d 100755
--- a/build-image.sh
+++ b/build-image.sh
@@ -91,6 +91,7 @@ podman tag rm "${REGISTRY}:latest" # Do not exit_err here. At least on first run
                                    # there is no latest tag to delete.
 
 # === Build the new image.
-podman build "${PODMAN_BUILD_ARGS[@]}" || exit_err "Build failed."
+podman build --build-arg=ROOTFS_FILENAME="${DISTFILES}/${ARCHIVE_FILE_NAME}" \
+  "${PODMAN_BUILD_ARGS[@]}" || exit_err "Build failed."
 
 # vim:fileencoding=utf-8:ts=4:syntax=bash:expandtab