diff --git a/tools/ci_setup.ml b/tools/ci_setup.ml
index 0cff22520..fd8bcaa87 100644
--- a/tools/ci_setup.ml
+++ b/tools/ci_setup.ml
@@ -245,9 +245,9 @@ let clone' delay ?branch ?commit nm src =
         (Printf.sprintf "cd jane-street/lib/%s && git checkout %s" nm commit)
 
 let () =
-  Out_channel.(
-    with_open_bin "jane-street/dune-workspace"
-    @@ fun ch -> output_string ch dune_workspace)
+  let ch = open_bin "jane-street/dune-workspace" in
+  output_string ch dune_workspace;
+  close_out ch
 
 let () =
   let js, others =