diff --git a/Dockerfile b/Dockerfile
index 985e46b..851b7da 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -21,6 +21,9 @@ FROM ${base_image} AS resource
 USER root
 
 COPY --from=busybox:uclibc /bin/mktemp /bin/
+COPY --from=busybox:uclibc /bin/mkdir /bin/
+COPY --from=busybox:uclibc /bin/sha256sum /bin/
+COPY --from=busybox:uclibc /bin/sha1sum /bin/
 COPY --from=stedolan/jq /usr/local/bin/jq /bin/
 COPY --from=tarampampam/curl /bin/curl /bin/
 
diff --git a/assets/in b/assets/in
index 59578d9..f48497c 100755
--- a/assets/in
+++ b/assets/in
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # vim: set ft=sh
 
 set -e
@@ -61,14 +61,14 @@ if ! [ "$sha256" = "null" ]; then
 fi
 
 if [ "$fetch_tarball" = "true" ]; then
-  pushd $destination >/dev/null
+  ( cd $destination
     curl --retry 5 --fail -L "$url" -o release.tgz
     if [ "$sha256" = "null" ]; then
       echo "$sha1  release.tgz" | sha1sum -c -
     else
       echo "$sha256  release.tgz" | sha256sum -c -
     fi
-  popd >/dev/null
+  )
 fi
 
 jq -n '{