diff --git a/src/lib/uTop.ml b/src/lib/uTop.ml
index 1ef863d..210b1cd 100644
--- a/src/lib/uTop.ml
+++ b/src/lib/uTop.ml
@@ -112,6 +112,65 @@ let get_ocaml_error_message exn =
   with _ ->
     ((0, 0), str)
 
+let collect_formatters buf pps f =
+  (* First flush all formatters. *)
+  List.iter (fun pp -> Format.pp_print_flush pp ()) pps;
+  (* Save all formatter functions. *)
+  let save = List.map (fun pp -> Format.pp_get_all_formatter_output_functions pp ()) pps in
+  let restore () =
+    List.iter2
+      (fun pp (out, flush, newline, spaces) ->
+         Format.pp_print_flush pp ();
+         Format.pp_set_all_formatter_output_functions pp ~out ~flush ~newline ~spaces)
+      pps save
+  in
+  (* Output functions. *)
+  let out str ofs len = Buffer.add_substring buf str ofs len in
+  let flush = ignore in
+  let newline () = Buffer.add_char buf '\n' in
+  let spaces n = for i = 1 to n do Buffer.add_char buf ' ' done in
+  (* Replace formatter functions. *)
+  let cols = (S.value size).cols in
+  List.iter
+    (fun pp ->
+       Format.pp_set_margin pp cols;
+       Format.pp_set_all_formatter_output_functions pp ~out ~flush ~newline ~spaces)
+    pps;
+  try
+    let x = f () in
+    restore ();
+    x
+  with exn ->
+    restore ();
+    raise exn
+
+let discard_formatters pps f =
+  (* First flush all formatters. *)
+  List.iter (fun pp -> Format.pp_print_flush pp ()) pps;
+  (* Save all formatter functions. *)
+  let save = List.map (fun pp -> Format.pp_get_all_formatter_output_functions pp ()) pps in
+  let restore () =
+    List.iter2
+      (fun pp (out, flush, newline, spaces) ->
+         Format.pp_print_flush pp ();
+         Format.pp_set_all_formatter_output_functions pp ~out ~flush ~newline ~spaces)
+      pps save
+  in
+  (* Output functions. *)
+  let out str ofs len = () in
+  let flush = ignore in
+  let newline = ignore in
+  let spaces = ignore in
+  (* Replace formatter functions. *)
+  List.iter (fun pp -> Format.pp_set_all_formatter_output_functions pp ~out ~flush ~newline ~spaces) pps;
+  try
+    let x = f () in
+    restore ();
+    x
+  with exn ->
+    restore ();
+    raise exn
+
 (* +-----------------------------------------------------------------+
    | Parsing                                                         |
    +-----------------------------------------------------------------+ *)
@@ -232,7 +291,7 @@ let check_phrase phrase =
         } in
         let check_phrase = Parsetree.Ptop_def [top_def] in
         try
-          let _ = Toploop.execute_phrase false null check_phrase in
+          let _ = discard_formatters [Format.err_formatter] (fun () -> Toploop.execute_phrase false null check_phrase) in
           (* The phrase is safe. *)
           Toploop.toplevel_env := env;
           Btype.backtrack snap;
diff --git a/src/lib/uTop.mli b/src/lib/uTop.mli
index aa0204e..f1f6533 100644
--- a/src/lib/uTop.mli
+++ b/src/lib/uTop.mli
@@ -216,6 +216,14 @@ val check_phrase : Parsetree.toplevel_phrase -> (location list * string) option
       If the result is [None] it is guaranteed that
       [Toploop.execute_phrase] won't raise any exception. *)
 
+val collect_formatters : Buffer.t -> Format.formatter list -> (unit -> 'a) -> 'a
+  (** [collect_formatters buf pps f] executes [f] and redirect
+      everything it prints on [pps] to [buf]. *)
+
+val discard_formatters : Format.formatter list -> (unit -> 'a) -> 'a
+  (** [discard_formatters pps f] executes [f], dropping everything it
+      prints on [pps]. *)
+
 (**/**)
 
 (* These variables are not used and deprecated: *)
diff --git a/src/lib/uTop_main.ml b/src/lib/uTop_main.ml
index aac244a..d06a0b2 100644
--- a/src/lib/uTop_main.ml
+++ b/src/lib/uTop_main.ml
@@ -73,21 +73,28 @@ let convert_locs str locs = List.map (fun (a, b) -> (index_of_offset str a, inde
    +-----------------------------------------------------------------+ *)
 
 let parse_and_check input eos_is_error =
-  match !UTop.parse_toplevel_phrase input eos_is_error with
-    | UTop.Error (locs, msg) ->
-        UTop.Error (convert_locs input locs, "Error: " ^ msg ^ "\n")
-    | UTop.Value phrase ->
-        match UTop.check_phrase phrase with
-          | None ->
-              UTop.Value phrase
-          | Some (locs, msg) ->
-              UTop.Error (convert_locs input locs, msg)
+  let buf = Buffer.create 32 in
+  let result =
+    UTop.collect_formatters buf [Format.err_formatter]
+      (fun () ->
+         match !UTop.parse_toplevel_phrase input eos_is_error with
+           | UTop.Error (locs, msg) ->
+               UTop.Error (convert_locs input locs, "Error: " ^ msg ^ "\n")
+           | UTop.Value phrase ->
+               match UTop.check_phrase phrase with
+                 | None ->
+                     UTop.Value phrase
+                 | Some (locs, msg) ->
+                     UTop.Error (convert_locs input locs, msg))
+  in
+  (result, Buffer.contents buf)
 
 (* Read a phrase. If the result is a value, it is guaranteed to by a
-   valid phrase (i.e. typable and compilable). *)
+   valid phrase (i.e. typable and compilable). It also returns
+   warnings printed parsing. *)
 class read_phrase ~term = object(self)
-  inherit [Parsetree.toplevel_phrase UTop.result] LTerm_read_line.engine ~history:(LTerm_history.contents UTop.history) () as super
-  inherit [Parsetree.toplevel_phrase UTop.result] LTerm_read_line.term term as super_term
+  inherit [Parsetree.toplevel_phrase UTop.result * string] LTerm_read_line.engine ~history:(LTerm_history.contents UTop.history) () as super
+  inherit [Parsetree.toplevel_phrase UTop.result * string] LTerm_read_line.term term as super_term
 
   val mutable return_value = None
 
@@ -135,7 +142,7 @@ class read_phrase ~term = object(self)
       LTerm_text.stylise_parenthesis styled position styles.style_paren
     else begin
       match return_value with
-        | Some (UTop.Error (locs, _)) ->
+        | Some (UTop.Error (locs, _), _) ->
             (* Highlight error locations. *)
             List.iter
               (fun (start, stop) ->
@@ -301,7 +308,10 @@ let rec loop term =
   let phrase_opt =
     Lwt_main.run (
       try_lwt
-        match_lwt read_phrase term with
+        lwt result, warnings = read_phrase term in
+        (* Print warnings before errors. *)
+        lwt () = Lwt_io.print warnings in
+        match result with
           | UTop.Value phrase ->
               return (Some phrase)
           | UTop.Error (_, msg) ->
@@ -527,9 +537,11 @@ module Emacs(M : sig end) = struct
 
   let process_input add_to_history eos_is_error =
     let input = read_data () in
-    match parse_and_check input eos_is_error with
+    let result, warnings = parse_and_check input eos_is_error in
+    match result with
       | UTop.Value phrase -> begin
           send "accept" "";
+          List.iter (send "stderr") (split_at ~trim:true '\n' warnings);
           if add_to_history then LTerm_history.add UTop.history input;
           (* Add Lwt_main.run to toplevel evals. *)
           let phrase = if UTop.get_auto_run_lwt () then insert_lwt_main_run phrase else phrase in
@@ -550,6 +562,7 @@ module Emacs(M : sig end) = struct
         end
       | UTop.Error (locs, msg) ->
           send "accept" (String.concat "," (List.map (fun (a, b) -> Printf.sprintf "%d,%d" a b) locs));
+          List.iter (send "stderr") (split_at ~trim:true '\n' warnings);
           if add_to_history then LTerm_history.add UTop.history input;
           List.iter (send "stderr") (split_at ~trim:true '\n' msg)