From 50d90e8703d421db773dcdfc3e114960d35796a2 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 10 Aug 2012 13:22:00 -0600
Subject: [PATCH] bug fix for thread improvement

Fixes a bug introduced with c89fa0cda7.
---
 src/racket/src/thread.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/racket/src/thread.c b/src/racket/src/thread.c
index dbcbcb9c96..1ef5f75863 100644
--- a/src/racket/src/thread.c
+++ b/src/racket/src/thread.c
@@ -3325,6 +3325,11 @@ Scheme_Object *scheme_call_as_nested_thread(int argc, Scheme_Object *argv[], voi
 
   scheme_current_thread = p;
 
+  if (!p->gc_prep_chain) {
+    p->gc_prep_chain = gc_prep_thread_chain;
+    gc_prep_thread_chain = p;
+  }
+
   if (p != scheme_main_thread)
     scheme_weak_resume_thread(p);