diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index b40d4f2abc..bb79829f50 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -3038,7 +3038,7 @@ extern char *scheme_convert_from_wchar(const wchar_t *ws);
 # define USE_SOCKETS_TCP
 #endif
 
-extern int scheme_active_but_sleeping;
+extern THREAD_LOCAL int scheme_active_but_sleeping;
 extern int scheme_file_open_count;
 
 typedef struct Scheme_Indexed_String {
diff --git a/src/mzscheme/src/thread.c b/src/mzscheme/src/thread.c
index 747cf3302c..6bbbbca3a9 100644
--- a/src/mzscheme/src/thread.c
+++ b/src/mzscheme/src/thread.c
@@ -153,16 +153,16 @@ void scheme_set_current_thread_ran_some() { scheme_current_thread->ran_some = 1;
 
 THREAD_LOCAL Scheme_Thread_Set *scheme_thread_set_top;
 
-static int num_running_threads = 1;
+static THREAD_LOCAL int num_running_threads = 1;
 
 #ifdef LINK_EXTENSIONS_BY_TABLE
 Scheme_Thread **scheme_current_thread_ptr;
 volatile int *scheme_fuel_counter_ptr;
 #endif
-static int swap_no_setjmp = 0;
+static THREAD_LOCAL int swap_no_setjmp = 0;
 
-static int thread_swap_count;
-static int did_gc_count;
+static THREAD_LOCAL int thread_swap_count;
+static THREAD_LOCAL int did_gc_count;
 
 static int init_load_on_demand = 1;
 
@@ -215,16 +215,16 @@ void (*scheme_wakeup_on_input)(void *fds);
 int (*scheme_check_for_break)(void);
 void (*scheme_on_atomic_timeout)(void);
 
-static int do_atomic = 0;
-static int missed_context_switch = 0;
-static int have_activity = 0;
-int scheme_active_but_sleeping = 0;
-static int thread_ended_with_activity;
+static THREAD_LOCAL int do_atomic = 0;
+static THREAD_LOCAL int missed_context_switch = 0;
+static THREAD_LOCAL int have_activity = 0;
+THREAD_LOCAL int scheme_active_but_sleeping = 0;
+static THREAD_LOCAL int thread_ended_with_activity;
 THREAD_LOCAL int scheme_no_stack_overflow;
 
-static int needs_sleep_cancelled;
+static THREAD_LOCAL int needs_sleep_cancelled;
 
-static int tls_pos = 0;
+static THREAD_LOCAL int tls_pos = 0;
 
 #ifdef MZ_PRECISE_GC
 extern long GC_get_memory_use(void *c);
@@ -247,15 +247,15 @@ typedef struct Thread_Cell {
 static Scheme_Object *read_symbol, *write_symbol, *execute_symbol, *delete_symbol, *exists_symbol;
 static Scheme_Object *client_symbol, *server_symbol;
 
-static Scheme_Object *nested_exn_handler;
+static THREAD_LOCAL Scheme_Object *nested_exn_handler;
 
-static Scheme_Object *closers;
+static THREAD_LOCAL Scheme_Object *closers;
 
-static Scheme_Object *thread_swap_callbacks,  *thread_swap_out_callbacks;
+static THREAD_LOCAL Scheme_Object *thread_swap_callbacks,  *thread_swap_out_callbacks;
 
-static Scheme_Object *recycle_cell;
-static Scheme_Object *maybe_recycle_cell;
-static int recycle_cc_count;
+static THREAD_LOCAL Scheme_Object *recycle_cell;
+static THREAD_LOCAL Scheme_Object *maybe_recycle_cell;
+static THREAD_LOCAL int recycle_cc_count;
 	
 static mz_jmp_buf main_init_error_buf;