diff --git a/src/Iter.ml b/src/Iter.ml
index 6e1a35a..8464bcb 100644
--- a/src/Iter.ml
+++ b/src/Iter.ml
@@ -1031,9 +1031,14 @@ module Map = struct
     let of_iter_ seq = fold (fun m (k, v) -> M.add k v m) M.empty seq
     let keys m = from_iter (fun k -> M.iter (fun x _ -> k x) m)
     let values m = from_iter (fun k -> M.iter (fun _ y -> k y) m)
+
+    [@@@ocaml.warning "-32"]
+
     let of_list l = of_iter_ (of_list l)
     let to_list x = to_list (to_iter_ x)
 
+    [@@@ocaml.warning "+32"]
+
     include M
 
     let to_iter = to_iter_
diff --git a/src/dune b/src/dune
index 957b57a..5666788 100644
--- a/src/dune
+++ b/src/dune
@@ -3,7 +3,7 @@
  (public_name iter)
  (wrapped false)
  (modules Iter IterLabels)
- (flags :standard -w +a -warn-error -a+8 -nolabels))
+ (flags :standard -w +a-4 -warn-error -a+8 -nolabels))
 
 (env
  (_