diff --git a/src/dune_rules/coq_module.ml b/src/dune_rules/coq_module.ml
index 7fef1dd25afd..927850ba9132 100644
--- a/src/dune_rules/coq_module.ml
+++ b/src/dune_rules/coq_module.ml
@@ -61,7 +61,7 @@ let obj_files x ~wrapper_name ~mode ~obj_dir =
       let cmxs_obj = cmxs_of_mod ~wrapper_name x in
       List.map
         ~f:(fun x ->
-          (Path.Build.relative vo_dir x, install_vo_dir ^ "/.coq_native/" ^ x))
+          (Path.Build.relative vo_dir x, Filename.(concat (concat install_vo_dir ".coq_native") x)))
         cmxs_obj
     | VoOnly -> []
   in