diff --git a/sw/ground_segment/cockpit/live.ml b/sw/ground_segment/cockpit/live.ml
index bcbc9b61de..540a5500a0 100644
--- a/sw/ground_segment/cockpit/live.ml
+++ b/sw/ground_segment/cockpit/live.ml
@@ -910,14 +910,12 @@ let listen_dl_value = fun () ->
     match ac.dl_settings_page with
         Some settings ->
           let csv = Pprz.string_assoc "values" vs in
-          let float_of_string_value = fun v -> match v with "?" -> None | _ -> Some v in
-          let values = Array.map float_of_string_value (Array.of_list (Str.split list_separator csv)) in
+          let string_value = fun v -> match v with "?" -> None | _ -> Some v in
+          let values = Array.map string_value (Array.of_list (Str.split list_separator csv)) in
           ac.dl_values <- values;
-          let float_of_value = fun v -> match v with None -> raise Not_found | Some x -> x in
           for i = 0 to min (Array.length values) settings#length - 1 do
             try
-              let v = float_of_value values.(i) in
-              settings#set i (try float_of_string v with _ -> failwith (sprintf "values.(%d)" i))
+              settings#set i values.(i)
             with _ -> ()
           done
       | None -> () in
diff --git a/sw/ground_segment/cockpit/page_settings.ml b/sw/ground_segment/cockpit/page_settings.ml
index 8e99856003..0dd1b0ef3f 100644
--- a/sw/ground_segment/cockpit/page_settings.ml
+++ b/sw/ground_segment/cockpit/page_settings.ml
@@ -31,6 +31,9 @@ class setting = fun (i:int) (xml:Xml.xml) (current_value:GMisc.label) set_defaul
 object
   method index = i
   method xml = xml
+  val mutable last_known_value = None
+  method last_known_value =
+    match last_known_value with None -> raise Not_found | Some v -> v
   method current_value =
     let auc = Pprz.alt_unit_coef_of_xml xml in
     let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
@@ -42,7 +45,11 @@ object
     else
       if current_value#text <> s then begin
         current_value#set_text s;
-        try set_default (float_of_string s) with Failure "float_of_string" -> ()
+        try
+          let v = float_of_string s in
+          last_known_value <- Some v;
+          set_default v
+        with Failure "float_of_string" -> ()
       end
 end
 
@@ -317,26 +324,31 @@ object (self)
   method widget = sw#coerce
   method length = length
   method keys = !keys
-  method set = fun i v ->
+  method set = fun i value ->
     if visible self#widget then
       let setting = variables.(i) in
-      let auc = Pprz.alt_unit_coef_of_xml setting#xml in
-      let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
-      let v = alt_a *. v +. alt_b in
-      let s = string_of_float v in
+      let s, v = match value with
+        | None -> "?", -1
+        | Some x ->
+          let v = try float_of_string x with _ -> failwith (sprintf "Pages.settings#set:wrong values.(%d) = %s" i x) in
+          let auc = Pprz.alt_unit_coef_of_xml setting#xml in
+          let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
+          let v = alt_a *. v +. alt_b in
+          string_of_float v, truncate v
+      in
       if i < 0 || i >= Array.length variables then
         failwith (sprintf "Pages.settings#set: %d out of bounnds (length=%d)" i (Array.length variables));
       let s =
         let values = values_of_dl_setting setting#xml in
         try
           let lower = int_of_string (ExtXml.attrib setting#xml "min") in
-          values.(truncate v - lower)
+          values.(v - lower)
         with
             _ -> s in
       setting#update s
   method assoc var = List.assoc var assocs
   method save = fun airframe_filename ->
-    let settings = Array.fold_right (fun setting r -> try (setting#index, setting#xml, setting#current_value)::r with _ -> r) variables [] in
+    let settings = Array.fold_right (fun setting r -> try (setting#index, setting#xml, setting#last_known_value)::r with _ -> r) variables [] in
     SaveSettings.popup airframe_filename (Array.of_list settings) do_change
 end
 
diff --git a/sw/ground_segment/cockpit/page_settings.mli b/sw/ground_segment/cockpit/page_settings.mli
index 52691f6a67..73b1600ba5 100644
--- a/sw/ground_segment/cockpit/page_settings.mli
+++ b/sw/ground_segment/cockpit/page_settings.mli
@@ -26,7 +26,7 @@
 class settings : ?visible:(GObj.widget -> bool) -> Xml.xml list -> (int -> float -> unit) -> (string -> GObj.widget -> unit) ->
   object
     method length : int (** Total number of settings *)
-    method set : int -> float -> unit (** Set the current value *)
+    method set : int -> string option -> unit (** Set the current value *)
     method assoc : string -> int
     method widget : GObj.widget
     method save : string -> unit
diff --git a/sw/ground_segment/tmtc/settings.ml b/sw/ground_segment/tmtc/settings.ml
index e8ae766efd..0569ccc69c 100644
--- a/sw/ground_segment/tmtc/settings.ml
+++ b/sw/ground_segment/tmtc/settings.ml
@@ -59,7 +59,7 @@ let one_ac = fun (notebook:GPack.notebook) ac_name ->
 
     (* Bind to values updates *)
     let get_dl_value = fun _sender vs ->
-      settings#set (Pprz.int_assoc "index" vs) (Pprz.float_assoc "value" vs)
+      settings#set (Pprz.int_assoc "index" vs) (Some (string_of_float (Pprz.float_assoc "value" vs)))
     in
     ignore (Tele_Pprz.message_bind "DL_VALUE" get_dl_value);