diff --git a/lib/top/dune b/lib/top/dune
index 01e161502..540c080f4 100644
--- a/lib/top/dune
+++ b/lib/top/dune
@@ -1,5 +1,6 @@
 (library
  (name        mdx_top)
  (public_name mdx.top)
+ (modes       byte)
  (preprocess (action (run %{bin:cppo} -V OCAML:%{ocaml_version} %{input-file})))
  (libraries   unix mdx compiler-libs compiler-libs.toplevel threads findlib.top))