diff --git a/Makefile b/Makefile
index 0c140e18..adf95352 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@ clean:
 	@dune clean
 
 test:
-	@dune runtest $(DUNE_OPTS)
+	@dune runtest $(DUNE_OPTS) --no-buffer
 
 test-autopromote:
 	@dune runtest $(DUNE_OPTS) --auto-promote
diff --git a/src/core/ws_pool.ml b/src/core/ws_pool.ml
index 7581636f..e10529d9 100644
--- a/src/core/ws_pool.ml
+++ b/src/core/ws_pool.ml
@@ -6,18 +6,7 @@ include Runner
 
 let ( let@ ) = ( @@ )
 
-module Id = struct
-  type t = unit ref
-  (** Unique identifier for a pool *)
-
-  let create () : t = Sys.opaque_identity (ref ())
-  let equal : t -> t -> bool = ( == )
-end
-
 type state = {
-  id_: Id.t;
-      (** Unique to this pool. Used to make sure tasks stay within the same
-          pool. *)
   active: bool A.t;  (** Becomes [false] when the pool is shutdown. *)
   mutable workers: worker_state array;  (** Fixed set of workers. *)
   main_q: WL.task_full Queue.t;
@@ -99,12 +88,15 @@ let schedule_in_main_queue (self : state) task : unit =
        longer permitted *)
     raise Shutdown
 
-let schedule_from_w (self : worker_state) (task : WL.task_full) : unit =
+let schedule_from_anywhere_ (st : state) (task : WL.task_full) : unit =
   match get_current_worker_ () with
-  | Some w when Id.equal self.st.id_ w.st.id_ ->
+  | Some w when st == w.st ->
     (* use worker from the same pool *)
     schedule_on_current_worker w task
-  | _ -> schedule_in_main_queue self.st task
+  | _ -> schedule_in_main_queue st task
+
+let schedule_from_w (w : worker_state) task : unit =
+  schedule_from_anywhere_ w.st task
 
 exception Got_task of WL.task_full
 
@@ -223,7 +215,8 @@ let as_runner_ (self : state) : t =
   Runner.For_runner_implementors.create
     ~shutdown:(fun ~wait () -> shutdown_ self ~wait)
     ~run_async:(fun ~fiber f ->
-      schedule_in_main_queue self @@ T_start { fiber; f })
+      let task = WL.T_start { fiber; f } in
+      schedule_from_anywhere_ self task)
     ~size:(fun () -> size_ self)
     ~num_tasks:(fun () -> num_tasks_ self)
     ()
@@ -240,7 +233,6 @@ type ('a, 'b) create_args =
 let create ?(on_init_thread = default_thread_init_exit_)
     ?(on_exit_thread = default_thread_init_exit_) ?(on_exn = fun _ _ -> ())
     ?num_threads ?name () : t =
-  let pool_id_ = Id.create () in
   let num_domains = Domain_pool_.max_number_of_domains () in
   let num_threads = Util_pool_.num_threads ?num_threads () in
 
@@ -249,7 +241,6 @@ let create ?(on_init_thread = default_thread_init_exit_)
 
   let pool =
     {
-      id_ = pool_id_;
       active = A.make true;
       workers = [||];
       main_q = Queue.create ();
diff --git a/test/dune b/test/dune
index 38b6a9c8..0e2a295c 100644
--- a/test/dune
+++ b/test/dune
@@ -20,3 +20,10 @@
   unix
   trace-tef
   trace))
+
+(test
+ (name t_fib_await_mem)
+ (package moonpool)
+ (enabled_if
+  (= %{system} linux))
+ (libraries moonpool))
diff --git a/test/t_fib_await_mem.ml b/test/t_fib_await_mem.ml
new file mode 100644
index 00000000..f255fdac
--- /dev/null
+++ b/test/t_fib_await_mem.ml
@@ -0,0 +1,54 @@
+(* regression test for #45 *)
+
+open Moonpool
+
+let ( let@ ) = ( @@ )
+
+let rec fib_direct x =
+  if x <= 1 then
+    1
+  else
+    fib_direct (x - 1) + fib_direct (x - 2)
+
+let cutoff = 8
+
+let rec fib_await ~on x : int Fut.t =
+  if x <= cutoff then
+    Fut.spawn ~on (fun () -> fib_direct x)
+  else
+    Fut.spawn ~on (fun () ->
+        let n1 = fib_await ~on (x - 1) in
+        let n2 = fib_await ~on (x - 2) in
+        let n1 = Fut.await n1 in
+        let n2 = Fut.await n2 in
+        n1 + n2)
+
+(** Read VmHWM (peak RSS in kB) from /proc/self/status. *)
+let get_vmhwm_kb () : int option =
+  let path = "/proc/self/status" in
+  match In_channel.with_open_bin path In_channel.input_all with
+  | exception Sys_error _ -> None
+  | content ->
+    let lines = String.split_on_char '\n' content in
+    List.find_map
+      (fun line -> Scanf.sscanf_opt line "VmHWM: %d kB" Fun.id)
+      lines
+
+let max_rss_bytes = 150_000_000
+
+let () =
+  let@ pool = Ws_pool.with_ ~num_threads:4 () in
+  let result = fib_await ~on:pool 40 |> Fut.wait_block_exn in
+  assert (result = 165580141);
+  match get_vmhwm_kb () with
+  | None ->
+    Printf.printf "fib 40 = %d (skip RSS check: no /proc/self/status)\n%!"
+      result
+  | Some hwm_kb ->
+    let hwm_bytes = hwm_kb * 1024 in
+    Printf.printf "fib 40 = %d, peak RSS = %d bytes\n%!" result hwm_bytes;
+    if hwm_bytes > max_rss_bytes then (
+      Printf.eprintf "FAIL: peak RSS %d bytes exceeds limit %d bytes\n%!"
+        hwm_bytes max_rss_bytes;
+      exit 1
+    )