diff --git a/src/racket/src/place.c b/src/racket/src/place.c
index 26c4ab8405..196e58f39c 100644
--- a/src/racket/src/place.c
+++ b/src/racket/src/place.c
@@ -1029,6 +1029,7 @@ void scheme_starting_child()
 
     signal_thread = mz_proc_thread_create(mz_proc_thread_signal_worker, NULL);
     mz_proc_thread_detach(signal_thread);
+    started_thread = 1;
   }
 
   pending_children++;