diff --git a/projects/miragesdk/src/sdk/IO.ml b/projects/miragesdk/src/sdk/IO.ml
index 7271e8962..13790e6d7 100644
--- a/projects/miragesdk/src/sdk/IO.ml
+++ b/projects/miragesdk/src/sdk/IO.ml
@@ -35,7 +35,7 @@ let pp ppf (Flow (name, _, _)) = Fmt.string ppf name
 
 type t = flow
 
-let forward ~src ~dst =
+let forward ?(verbose=false) ~src ~dst =
   let rec loop () =
     read src >>= function
     | Ok `Eof ->
@@ -45,8 +45,12 @@ let forward ~src ~dst =
       Log.err (fun l -> l "forward[%a => %a] %a" pp src pp dst pp_error e);
       Lwt.return_unit
     | Ok (`Data buf) ->
-      Log.debug (fun l -> l "forward[%a => %a] %d bytes"
-                    pp src pp dst @@ Cstruct.len buf);
+      Log.debug (fun l ->
+          let payload =
+            if verbose then Fmt.strf "[%S]" @@ Cstruct.to_string buf
+            else Fmt.strf "%d bytes" (Cstruct.len buf)
+          in
+          l "forward[%a => %a] %s" pp src pp dst payload);
       write dst buf >>= function
       | Ok ()   -> loop ()
       | Error e ->
@@ -56,8 +60,8 @@ let forward ~src ~dst =
   in
   loop ()
 
-let proxy f1 f2 =
+let proxy ?verbose f1 f2 =
   Lwt.join [
-    forward ~src:f1 ~dst:f2;
-    forward ~src:f2 ~dst:f1;
+    forward ?verbose ~src:f1 ~dst:f2;
+    forward ?verbose ~src:f2 ~dst:f1;
   ]
diff --git a/projects/miragesdk/src/sdk/IO.mli b/projects/miragesdk/src/sdk/IO.mli
index 2883e34d2..fa1e0450d 100644
--- a/projects/miragesdk/src/sdk/IO.mli
+++ b/projects/miragesdk/src/sdk/IO.mli
@@ -12,10 +12,14 @@ val create: (module Mirage_flow_lwt.S with type flow = 'a) -> 'a -> string -> fl
 val pp: flow Fmt.t
 (** [pp] is the pretty-printer for IO flows. *)
 
-val forward: src:t -> dst:t -> unit Lwt.t
-(** [forward ~src ~dst] forwards writes from [src] to [dst]. Block
-    until either [src] or [dst] is closed. *)
+val forward: ?verbose:bool -> src:t -> dst:t -> unit Lwt.t
+(** [forward ?verbose ~src ~dst] forwards writes from [src] to
+    [dst]. Block until either [src] or [dst] is closed. If [verbose]
+    is set (by default it is not), show the raw flow in debug mode,
+    otherwise just show the lenght. *)
 
-val proxy: t -> t -> unit Lwt.t
-(** [proxy x y] is the same as [forward x y <*> forward y x]. Block
-    until both flows are closed. *)
+val proxy: ?verbose:bool -> t -> t -> unit Lwt.t
+(** [proxy ?verbose x y] is the same as [forward x y <*> forward y
+    x]. Block until both flows are closed. If [verbose] is set (by
+    default it is not), show the raw flow in debug mode, otherwise
+    just show the lenght. *)
diff --git a/projects/miragesdk/src/sdk/init.ml b/projects/miragesdk/src/sdk/init.ml
index 1ef40cb05..d0590cd28 100644
--- a/projects/miragesdk/src/sdk/init.ml
+++ b/projects/miragesdk/src/sdk/init.ml
@@ -291,11 +291,11 @@ let exec_and_forward ?(handlers=block_for_ever) ~pid ~cmd ~net ~ctl t =
   Lwt.pick ([
       wait ();
       (* data *)
-      IO.proxy net priv_net;
+      IO.proxy ~verbose:true net priv_net;
 
       (* redirect the calf stdout to the shim stdout *)
-      IO.forward ~src:priv_stdout ~dst:Fd.(flow stdout);
-      IO.forward ~src:priv_stderr ~dst:Fd.(flow stderr);
+      IO.forward ~verbose:false ~src:priv_stdout ~dst:Fd.(flow stdout);
+      IO.forward ~verbose:false ~src:priv_stderr ~dst:Fd.(flow stderr);
       (* TODO: Init.Fd.forward ~src:Init.Pipe.(priv metrics)
          ~dst:Init.Fd.metric; *)
       ctl priv_ctl;