diff --git a/src/lib/io/io.h b/src/lib/io/io.h
index b54a7b4b6c98..0e50c96fc5de 100644
--- a/src/lib/io/io.h
+++ b/src/lib/io/io.h
@@ -42,6 +42,7 @@ typedef struct fr_listen fr_listen_t;
  */
 typedef enum fr_io_action_t {
 	FR_IO_ACTION_RUN,
+	FR_IO_ACTION_DUP,
 	FR_IO_ACTION_DONE,
 } fr_io_action_t;
 
diff --git a/src/lib/io/worker.c b/src/lib/io/worker.c
index 3b801d973f61..7372de70a05d 100644
--- a/src/lib/io/worker.c
+++ b/src/lib/io/worker.c
@@ -887,12 +887,23 @@ static REQUEST *fr_worker_get_request(fr_worker_t *worker, fr_time_t now)
 		 *
 		 *	@todo - fix the channel code to do queue
 		 *	depth, and not sequence / ack.
-		 *
-		 *	@todo - send DUP signal to old request!
 		 */
 		if (old->async->recv_time == request->async->recv_time) {
 			fr_channel_null_reply(request->async->channel);
 			talloc_free(request);
+
+			/*
+			 *	Signal there's a dup, and ignore the
+			 *	return code.  We don't bother replying
+			 *	here, as an FD event or timer will
+			 *	wake up the request, and cause it to
+			 *	continue.
+			 *
+			 *	@todo - the old request is NOT
+			 *	running, but is yielded.  It MAY clean
+			 *	itself up, or do something...
+			 */
+			(void) old->async->process(old, FR_IO_ACTION_DUP);
 			return NULL;
 		}