diff --git a/src/core/fut.ml b/src/core/fut.ml
index 847a1156..2ae34996 100644
--- a/src/core/fut.ml
+++ b/src/core/fut.ml
@@ -3,23 +3,23 @@ module C = Picos.Computation
 
 type 'a or_error = ('a, Exn_bt.t) result
 type 'a waiter = 'a or_error -> unit
-type 'a t = { st: 'a C.t } [@@unboxed]
+type 'a t = 'a C.t
 type 'a promise = 'a t
 
 let[@inline] make_promise () : _ t =
-  let fut = { st = C.create ~mode:`LIFO () } in
+  let fut = C.create ~mode:`LIFO () in
   fut
 
 let make () =
   let fut = make_promise () in
   fut, fut
 
-let[@inline] return x : _ t = { st = C.returned x }
+let[@inline] return x : _ t = C.returned x
 
 let[@inline] fail exn bt : _ t =
-  let st = C.create () in
-  C.cancel st exn bt;
-  { st }
+  let fut = C.create () in
+  C.cancel fut exn bt;
+  fut
 
 let[@inline] fail_exn_bt ebt = fail (Exn_bt.exn ebt) (Exn_bt.bt ebt)
 
@@ -27,32 +27,32 @@ let[@inline] of_result = function
   | Ok x -> return x
   | Error ebt -> fail_exn_bt ebt
 
-let[@inline] is_resolved self : bool = not (C.is_running self.st)
+let[@inline] is_resolved self : bool = not (C.is_running self)
 let is_done = is_resolved
-let[@inline] peek self : _ option = C.peek self.st
-let[@inline] raise_if_failed self : unit = C.check self.st
+let peek : 'a t -> _ option = C.peek
+let raise_if_failed : _ t -> unit = C.check
 
 let[@inline] is_success self =
-  match C.peek_exn self.st with
+  match C.peek_exn self with
   | _ -> true
   | exception _ -> false
 
-let[@inline] is_failed self = C.is_canceled self.st
+let is_failed : _ t -> bool = C.is_canceled
 
 exception Not_ready
 
 let[@inline] get_or_fail self =
-  match C.peek self.st with
+  match C.peek self with
   | Some x -> x
   | None -> raise Not_ready
 
 let[@inline] get_or_fail_exn self =
-  match C.peek_exn self.st with
+  match C.peek_exn self with
   | x -> x
   | exception C.Running -> raise Not_ready
 
 let[@inline] peek_or_assert_ (self : 'a t) : 'a =
-  match C.peek_exn self.st with
+  match C.peek_exn self with
   | x -> x
   | exception C.Running -> assert false
 
@@ -67,32 +67,32 @@ let on_result (self : _ t) (f : _ waiter) : unit =
   let trigger =
     (Trigger.from_action f self on_result_cb_ [@alert "-handler"])
   in
-  if not (C.try_attach self.st trigger) then on_result_cb_ () f self
+  if not (C.try_attach self trigger) then on_result_cb_ () f self
 
 let on_result_ignore_cb_ _tr f (self : _ t) =
-  f (Picos.Computation.canceled self.st)
+  f (Picos.Computation.canceled self)
 
 let on_result_ignore (self : _ t) f : unit =
-  if Picos.Computation.is_running self.st then (
+  if Picos.Computation.is_running self then (
     let trigger =
       (Trigger.from_action f self on_result_ignore_cb_ [@alert "-handler"])
     in
-    if not (C.try_attach self.st trigger) then on_result_ignore_cb_ () f self
+    if not (C.try_attach self trigger) then on_result_ignore_cb_ () f self
   ) else
     on_result_ignore_cb_ () f self
 
 let[@inline] fulfill_idempotent self r =
   match r with
-  | Ok x -> C.return self.st x
-  | Error ebt -> C.cancel self.st (Exn_bt.exn ebt) (Exn_bt.bt ebt)
+  | Ok x -> C.return self x
+  | Error ebt -> C.cancel self (Exn_bt.exn ebt) (Exn_bt.bt ebt)
 
 exception Already_fulfilled
 
 let fulfill (self : _ t) (r : _ result) : unit =
   let ok =
     match r with
-    | Ok x -> C.try_return self.st x
-    | Error ebt -> C.try_cancel self.st (Exn_bt.exn ebt) (Exn_bt.bt ebt)
+    | Ok x -> C.try_return self x
+    | Error ebt -> C.try_cancel self (Exn_bt.exn ebt) (Exn_bt.bt ebt)
   in
   if not ok then raise Already_fulfilled
 
@@ -104,10 +104,10 @@ let spawn ~on f : _ t =
   let task () =
     try
       let res = f () in
-      C.return fut.st res
+      C.return fut res
     with exn ->
       let bt = Printexc.get_raw_backtrace () in
-      C.cancel fut.st exn bt
+      C.cancel fut exn bt
   in
 
   Runner.run_async on task;
@@ -380,7 +380,7 @@ let for_list ~on l f : unit t =
 let push_queue_ _tr q () = Bb_queue.push q ()
 
 let wait_block_exn (self : 'a t) : 'a =
-  match C.peek_exn self.st with
+  match C.peek_exn self with
   | x -> x (* fast path *)
   | exception C.Running ->
     let real_block () =
@@ -394,7 +394,7 @@ let wait_block_exn (self : 'a t) : 'a =
       assert attached;
 
       (* blockingly wait for trigger if computation didn't complete in the mean time *)
-      if C.try_attach self.st trigger then Bb_queue.pop q;
+      if C.try_attach self trigger then Bb_queue.pop q;
 
       (* trigger was signaled! computation must be done*)
       peek_or_assert_ self
@@ -406,7 +406,7 @@ let wait_block_exn (self : 'a t) : 'a =
       if i = 0 then
         real_block ()
       else (
-        match C.peek_exn self.st with
+        match C.peek_exn self with
         | x -> x
         | exception C.Running ->
           Domain_.relax ();
@@ -426,12 +426,12 @@ let wait_block self =
 
 let await (self : 'a t) : 'a =
   (* fast path: peek *)
-  match C.peek_exn self.st with
+  match C.peek_exn self with
   | res -> res
   | exception C.Running ->
     let trigger = Trigger.create () in
     (* suspend until the future is resolved *)
-    if C.try_attach self.st trigger then
+    if C.try_attach self trigger then
       Option.iter Exn_bt.raise @@ Trigger.await trigger;
 
     (* un-suspended: we should have a result! *)
@@ -453,5 +453,5 @@ module Infix_local = Infix [@@deprecated "use Infix"]
 
 module Private_ = struct
   let[@inline] unsafe_promise_of_fut x = x
-  let[@inline] as_computation self = self.st
+  let[@inline] as_computation self = self
 end
diff --git a/src/core/fut.mli b/src/core/fut.mli
index b6682b1c..c9c357f5 100644
--- a/src/core/fut.mli
+++ b/src/core/fut.mli
@@ -19,7 +19,7 @@
 
 type 'a or_error = ('a, Exn_bt.t) result
 
-type 'a t
+type 'a t = 'a Picos.Computation.t
 (** A future with a result of type ['a]. *)
 
 type 'a promise = private 'a t