diff --git a/src/mzscheme/gc2/newgc.c b/src/mzscheme/gc2/newgc.c
index 6771384a35..bd6eda90c3 100644
--- a/src/mzscheme/gc2/newgc.c
+++ b/src/mzscheme/gc2/newgc.c
@@ -1865,7 +1865,6 @@ void GC_construct_child_gc() {
 }
 
 static inline void save_globals_to_gc(NewGC *gc) {
-  gc->saved_mark_stack              = mark_stack;
   gc->saved_GC_variable_stack       = GC_variable_stack;
   gc->saved_GC_gen0_alloc_page_ptr  = GC_gen0_alloc_page_ptr;
   gc->saved_GC_gen0_alloc_page_end  = GC_gen0_alloc_page_end;
@@ -1873,7 +1872,6 @@ static inline void save_globals_to_gc(NewGC *gc) {
 }
 
 static inline void restore_globals_from_gc(NewGC *gc) {
-  mark_stack              = gc->saved_mark_stack;
   GC_variable_stack       = gc->saved_GC_variable_stack;
   GC_gen0_alloc_page_ptr  = gc->saved_GC_gen0_alloc_page_ptr;
   GC_gen0_alloc_page_end  = gc->saved_GC_gen0_alloc_page_end;
diff --git a/src/mzscheme/src/env.c b/src/mzscheme/src/env.c
index 312af4e013..8336e4776e 100644
--- a/src/mzscheme/src/env.c
+++ b/src/mzscheme/src/env.c
@@ -144,7 +144,7 @@ int scheme_is_module_begin_env(Scheme_Comp_Env *env);
 Scheme_Env *scheme_engine_instance_init();
 Scheme_Env *scheme_place_instance_init();
 static void place_instance_init_pre_kernel();
-static Scheme_Env *place_instance_init_post_kernel();
+static Scheme_Env *place_instance_init_post_kernel(int initial_main_os_thread);
 
 #ifdef MZ_PRECISE_GC
 static void register_traversers(void);
@@ -361,7 +361,7 @@ Scheme_Env *scheme_engine_instance_init() {
   place_instance_init_pre_kernel(stack_base);
   make_kernel_env();
   scheme_init_parameterization_readonly_globals();
-  env = place_instance_init_post_kernel();
+  env = place_instance_init_post_kernel(1);
 
   return env;
 }
@@ -428,7 +428,7 @@ Scheme_Env *scheme_get_unsafe_env() {
   return unsafe_env;
 }
 
-static Scheme_Env *place_instance_init_post_kernel() {
+static Scheme_Env *place_instance_init_post_kernel(int initial_main_os_thread) {
   Scheme_Env *env;
   /* error handling and buffers */
   /* this check prevents initializing orig ports twice for the first initial
@@ -442,7 +442,7 @@ static Scheme_Env *place_instance_init_post_kernel() {
   scheme_init_logger();
   scheme_init_eval_places();
   scheme_init_regexp_places();
-  scheme_init_stx_places();
+  scheme_init_stx_places(initial_main_os_thread);
   scheme_init_sema_places();
   scheme_init_gmp_places();
   scheme_alloc_global_fdset();
@@ -497,7 +497,7 @@ static Scheme_Env *place_instance_init_post_kernel() {
 
 Scheme_Env *scheme_place_instance_init(void *stack_base) {
   place_instance_init_pre_kernel(stack_base);
-  return place_instance_init_post_kernel();
+  return place_instance_init_post_kernel(0);
 }
 
 void scheme_place_instance_destroy() {
diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index ff26738435..5c4c3b6989 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -230,7 +230,7 @@ void scheme_init_print_buffers_places(void);
 void scheme_init_eval_places(void);
 void scheme_init_port_places(void);
 void scheme_init_regexp_places(void);
-void scheme_init_stx_places(void);
+void scheme_init_stx_places(int initial_main_os_thread);
 void scheme_init_fun_places(void);
 void scheme_init_sema_places(void);
 void scheme_init_gmp_places(void);
diff --git a/src/mzscheme/src/stxobj.c b/src/mzscheme/src/stxobj.c
index 76c90aea1e..f50b26835b 100644
--- a/src/mzscheme/src/stxobj.c
+++ b/src/mzscheme/src/stxobj.c
@@ -631,7 +631,7 @@ void scheme_init_stx(Scheme_Env *env)
   scheme_install_type_reader2(scheme_free_id_info_type, read_free_id_info_prefix);
 }
 
-void scheme_init_stx_places() {
+void scheme_init_stx_places(int initial_main_os_thread) {
   REGISTER_SO(last_phase_shift);
   REGISTER_SO(nominal_ipair_cache);
   REGISTER_SO(quick_hash_table);
@@ -639,6 +639,14 @@ void scheme_init_stx_places() {
   REGISTER_SO(than_id_marks_ht);
   REGISTER_SO(interned_skip_ribs);
   REGISTER_SO(unsealed_dependencies);
+  
+  if (!initial_main_os_thread) {
+    REGISTER_SO(mark_id);
+    REGISTER_SO(current_rib_timestamp);
+    mark_id = scheme_make_integer(0);
+    current_rib_timestamp = scheme_make_integer(0);
+  }
+
   interned_skip_ribs = scheme_make_weak_equal_table();
 }