diff --git a/src/client/generic_consumer.ml b/src/client/generic_consumer.ml
index c54ed78e..07b49488 100644
--- a/src/client/generic_consumer.ml
+++ b/src/client/generic_consumer.ml
@@ -83,13 +83,19 @@ end = struct
 
   (** Shutdown one worker, when the queue is closed *)
   let shutdown_worker (self : state) : unit =
-    (* let tid = Thread.id @@ Thread.self () in
-       Printf.eprintf "worker %d: shutting down\n%!" tid; *)
     if Atomic.fetch_and_add self.n_workers (-1) = 1 then (
-      (* we were the last worker *)
-      (* Printf.eprintf "worker %d: last one!\n%!" tid; *)
+      (* we were the last worker, we can shut down the whole consumer *)
       Atomic.set self.status Stopped;
-      Aswitch.turn_off self.active_trigger
+      Aswitch.turn_off self.active_trigger;
+
+      (* sanity check about the queue, which should be drained *)
+      let size_q = Bounded_queue.Recv.size self.q in
+      if size_q > 0 then
+        Printf.eprintf
+          "otel: warning: workers exited but work queue still contains %d \
+           elements\n\
+           %!"
+          size_q
     )
 
   let send_signals (self : state) (sender : Sender.t) ~backoff