diff --git a/dune b/dune
index 18bee1e5..655216a2 100644
--- a/dune
+++ b/dune
@@ -8,4 +8,5 @@
  (alias runtest)
  (package containers-data)
  (enabled_if (= %{system} "linux"))
+ (locks /ctest)
  (action (diff README.md README.md.corrected)))
diff --git a/src/mdx_runner.ml b/src/mdx_runner.ml
index e485d0ca..719a366d 100644
--- a/src/mdx_runner.ml
+++ b/src/mdx_runner.ml
@@ -20,7 +20,7 @@ let () =
       printf "warning: ocaml-mdx exited with code %d\n" e;
       just_copy();
     ) else (
-      print_endline "ocaml-mdx returned 0";
+      print_endline "ocaml-mdx returned 0 ✔";
     )
   with Sys_error e ->
     printf "error when running mdx: %s\n" e;