diff --git a/src/mzscheme/src/env.c b/src/mzscheme/src/env.c
index 8c4de23ddf..bb8f7fd4d5 100644
--- a/src/mzscheme/src/env.c
+++ b/src/mzscheme/src/env.c
@@ -437,6 +437,7 @@ static Scheme_Env *place_instance_init_post_kernel() {
   scheme_init_eval_places();
   scheme_init_regexp_places();
   scheme_init_stx_places();
+  scheme_init_sema_places();
 
   env = scheme_make_empty_env();
   scheme_set_param(scheme_current_config(), MZCONFIG_ENV, (Scheme_Object *)env); 
diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index a4b7d58d91..58adacc95f 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -231,6 +231,7 @@ void scheme_init_port_places(void);
 void scheme_init_regexp_places(void);
 void scheme_init_stx_places(void);
 void scheme_init_fun_places(void);
+void scheme_init_sema_places(void);
 void scheme_init_print_global_constants(void);
 
 void register_network_evts();
@@ -333,7 +334,7 @@ extern Scheme_Object *scheme_stack_dump_key;
 
 extern Scheme_Object *scheme_default_prompt_tag;
 
-extern Scheme_Object *scheme_system_idle_channel;
+extern THREAD_LOCAL Scheme_Object *scheme_system_idle_channel;
 
 extern Scheme_Object *scheme_input_port_property, *scheme_output_port_property;
 
diff --git a/src/mzscheme/src/sema.c b/src/mzscheme/src/sema.c
index 0e927e49a8..aaecd491a6 100644
--- a/src/mzscheme/src/sema.c
+++ b/src/mzscheme/src/sema.c
@@ -24,7 +24,7 @@
 #ifndef NO_SCHEME_THREADS
 
 Scheme_Object *scheme_always_ready_evt;
-Scheme_Object *scheme_system_idle_channel;
+THREAD_LOCAL Scheme_Object *scheme_system_idle_channel;
 
 static Scheme_Object *make_sema(int n, Scheme_Object **p);
 static Scheme_Object *semap(int n, Scheme_Object **p);
@@ -196,9 +196,6 @@ void scheme_init_sema(Scheme_Env *env)
   o->type = scheme_thread_recv_evt_type;
   thread_recv_evt = o;
 
-  REGISTER_SO(scheme_system_idle_channel);
-  scheme_system_idle_channel = scheme_make_channel();
-
   scheme_add_evt(scheme_sema_type, sema_ready, NULL, NULL, 0);
   scheme_add_evt_through_sema(scheme_semaphore_repost_type, sema_for_repost, NULL);
   scheme_add_evt(scheme_channel_type, (Scheme_Ready_Fun)channel_get_ready, NULL, NULL, 1);
@@ -210,6 +207,11 @@ void scheme_init_sema(Scheme_Env *env)
   scheme_add_evt(scheme_thread_recv_evt_type, (Scheme_Ready_Fun)thread_recv_ready, NULL, NULL, 0);
 }
 
+void scheme_init_sema_places() {
+  REGISTER_SO(scheme_system_idle_channel);
+  scheme_system_idle_channel = scheme_make_channel();
+}
+
 Scheme_Object *scheme_make_sema(long v)
 {
   Scheme_Sema *sema;