diff --git a/src/lwt/dune b/src/lwt/dune
index c6bb5ab3..93c86e61 100644
--- a/src/lwt/dune
+++ b/src/lwt/dune
@@ -5,6 +5,7 @@
   (>= %{ocaml_version} 5.0))
  (libraries
   (re_export moonpool)
+  moonpool.fib
   picos
   (re_export lwt)
   lwt.unix))
diff --git a/src/lwt/moonpool_lwt.ml b/src/lwt/moonpool_lwt.ml
index 9fa62582..1e1086c0 100644
--- a/src/lwt/moonpool_lwt.ml
+++ b/src/lwt/moonpool_lwt.ml
@@ -49,9 +49,9 @@ module Scheduler_state = struct
   let[@inline never] add_action_from_another_thread_ (self : st) f : unit =
     Mutex.lock self.mutex;
     Queue.push f self.actions_from_other_threads;
+    Mutex.unlock self.mutex;
     if not (Atomic.exchange self.has_notified true) then
-      Lwt_unix.send_notification self.notification;
-    Mutex.unlock self.mutex
+      Lwt_unix.send_notification self.notification
 
   let[@inline] on_lwt_thread_ (self : st) : bool =
     Thread.id (Thread.self ()) = self.thread
@@ -73,9 +73,10 @@ module Scheduler_state = struct
         failwith "moonpool-lwt: cleanup from the wrong thread";
       Option.iter Lwt_main.Enter_iter_hooks.remove st.enter_hook;
       Option.iter Lwt_main.Leave_iter_hooks.remove st.leave_hook;
+      Lwt_unix.stop_notification st.notification;
 
       Atomic.set cur_st None
-    | _ -> ()
+    | None -> failwith "moonpool-lwt: cleanup failed (no current active state)"
 end
 
 module Ops = struct
@@ -290,7 +291,7 @@ let[@inline] is_setup () = Option.is_some @@ Atomic.get Scheduler_state.cur_st
 let spawn_lwt f : _ Lwt.t =
   let st = Main_state.get_st () in
   let lwt_fut, lwt_prom = Lwt.wait () in
-  M.Runner.run_async st.as_runner (fun () ->
+  Moonpool_fib.spawn_top_ignore ~on:st.as_runner (fun () ->
       try
         let x = f () in
         Lwt.wakeup lwt_prom x