diff --git a/src/racket/src/thread.c b/src/racket/src/thread.c
index d7475a646d..22e2198252 100644
--- a/src/racket/src/thread.c
+++ b/src/racket/src/thread.c
@@ -3228,9 +3228,6 @@ Scheme_Object *scheme_call_as_nested_thread(int argc, Scheme_Object *argv[], voi
   scheme_first_thread->prev = np;
   scheme_first_thread = np;
 
-  np->gc_prep_chain = gc_prep_thread_chain;
-  gc_prep_thread_chain = np;
-
   np->t_set_parent = p->t_set_parent;
   schedule_in_set((Scheme_Object *)np, np->t_set_parent);
 
@@ -3283,6 +3280,9 @@ Scheme_Object *scheme_call_as_nested_thread(int argc, Scheme_Object *argv[], voi
 #endif
   }
 
+  np->gc_prep_chain = gc_prep_thread_chain;
+  gc_prep_thread_chain = np;
+
 #ifdef RUNSTACK_IS_GLOBAL
   MZ_CONT_MARK_STACK = np->cont_mark_stack;
   MZ_CONT_MARK_POS = np->cont_mark_pos;