diff --git a/src/dune_pkg/rev_store.ml b/src/dune_pkg/rev_store.ml
index ee9f6680ac1..7f1fbdfd5a2 100644
--- a/src/dune_pkg/rev_store.ml
+++ b/src/dune_pkg/rev_store.ml
@@ -48,13 +48,19 @@ let show { dir } (Rev rev) path =
 
 let load_or_create ~dir =
   let t = { dir } in
-  (* TODO might as well double check it's a directory *)
-  match Path.exists dir with
-  | true -> Fiber.return t
-  | false ->
-    Path.mkdir_p dir;
-    let+ () = run t [ "init"; "--bare" ] in
-    t
+  let* () = Fiber.return () in
+  let+ () =
+    match Fpath.mkdir_p (Path.to_string dir) with
+    | Already_exists -> Fiber.return ()
+    | Created -> run t [ "init"; "--bare" ]
+    | exception Unix.Unix_error (e, x, y) ->
+      User_error.raise
+        [ Pp.textf "%s isn't a directory" (Path.to_string_maybe_quoted dir)
+        ; Pp.textf "reason: %s" (Unix_error.Detailed.to_string_hum (e, x, y))
+        ]
+        ~hints:[ Pp.text "delete this file or check its permissions" ]
+  in
+  t
 ;;
 
 module Remote = struct