diff --git a/src/repo/learnocaml_process_exercise_repository.ml b/src/repo/learnocaml_process_exercise_repository.ml
index df2cbb627..43c964c3d 100644
--- a/src/repo/learnocaml_process_exercise_repository.ml
+++ b/src/repo/learnocaml_process_exercise_repository.ml
@@ -230,6 +230,8 @@ let main dest_dir =
              Lwt_list.map_p,
              spawn_grader
          in
+         let static_dir = String.concat Filename.dir_sep [dest_dir; "static"] in
+         Lwt_utils.mkdir_p static_dir >>= fun () ->
          listmap (fun (id, ex_dir, exercise, json_path, changed, dump_outputs,dump_reports) ->
              let dst_ex_dir = String.concat Filename.dir_sep [dest_dir; "static"; id] in
              Lwt_utils.mkdir_p dst_ex_dir >>= fun () ->
diff --git a/tests/runtests.sh b/tests/runtests.sh
index c1f06b506..8674e6a6e 100755
--- a/tests/runtests.sh
+++ b/tests/runtests.sh
@@ -234,7 +234,7 @@ do
 
     if ! ( set -x; docker run --entrypoint '' \
            -v "$(realpath "$corpus"):/repository" \
-           learn-ocaml /bin/sh -c "learn-ocaml --repo=/repository build" ); then
+           learn-ocaml /bin/sh -c "learn-ocaml --repo=/repository build -j 2" ); then
         red "Failed to build $corpus"
         exit 1
     fi