diff --git a/sw/logalizer/plot.ml b/sw/logalizer/plot.ml
index c365f1ca47..9c9a1acaf3 100644
--- a/sw/logalizer/plot.ml
+++ b/sw/logalizer/plot.ml
@@ -273,8 +273,8 @@ let write_kml = fun plot log_name values ->
   let l = ref [] in
   let t_min = plot#min_x ()
   and t_max = plot#max_x () in
-  let t_min = if t_min = max_float then min_float else t_min in
-  let t_max = if t_max = min_float then max_float else t_max in
+  let t_min = if t_min = max_float then -. max_float else t_min in
+  let t_max = if t_max = -. max_float then max_float else t_max in
   for i = 0 to Array.length xs - 1 do
     let t = fst xs.(i) in
     if t_min <= t && t < t_max then
diff --git a/sw/logalizer/plotter.ml b/sw/logalizer/plotter.ml
index 25e4b4754a..c982ba73f3 100644
--- a/sw/logalizer/plotter.ml
+++ b/sw/logalizer/plotter.ml
@@ -120,7 +120,7 @@ class plot = fun ~size ~width ~height ~packing () ->
     method reset () =
       if auto_scale then begin
 	min <- max_float;
-	max <- min_float
+	max <- -. max_float
       end;
       Hashtbl.iter (fun _ a ->
 	a.index <- 0;