diff --git a/src/racket/sconfig.h b/src/racket/sconfig.h
index 3188560562..f5b923c5c5 100644
--- a/src/racket/sconfig.h
+++ b/src/racket/sconfig.h
@@ -763,9 +763,13 @@
 # define MZ_USE_JIT_I386
 # ifndef MZ_NO_JIT_SSE
 #  define MZ_USE_JIT_SSE
-#  define ASM_DBLPREC_CONTROL_87
 # endif
 #endif
+
+#ifdef MZ_NO_JIT_SSE
+# define ASM_DBLPREC_CONTROL_87
+#endif
+
 # define MZ_JIT_USE_MPROTECT
 
 # define FLAGS_ALREADY_SET
diff --git a/src/racket/src/future.c b/src/racket/src/future.c
index 41caccb141..9dc48c1095 100644
--- a/src/racket/src/future.c
+++ b/src/racket/src/future.c
@@ -2151,6 +2151,8 @@ void *worker_thread_future_loop(void *arg)
     mzrt_mutex_unlock(fs->future_mutex);
   */
 
+  scheme_configure_floating_point();
+
   mzrt_sema_create(&fts->worker_can_continue_sema, 0);
 
   scheme_use_rtcall = 1;
diff --git a/src/racket/src/number.c b/src/racket/src/number.c
index bd5b56e506..8ac33b3074 100644
--- a/src/racket/src/number.c
+++ b/src/racket/src/number.c
@@ -213,32 +213,11 @@ static void to_extended_prec(void)
 }
 #endif
 
-void
-scheme_init_number (Scheme_Env *env)
-{
-  Scheme_Object *p;
 
-  REGISTER_SO(scheme_pi);
-  REGISTER_SO(scheme_half_pi);
-  REGISTER_SO(scheme_zerod);
-  REGISTER_SO(scheme_nzerod);
-#ifdef MZ_USE_SINGLE_FLOATS
-  REGISTER_SO(scheme_single_pi);
-  REGISTER_SO(scheme_zerof);
-  REGISTER_SO(scheme_nzerof);
-#endif
-  REGISTER_SO(scheme_plus_i);
-  REGISTER_SO(scheme_minus_i);
-  REGISTER_SO(scheme_inf_object);
-  REGISTER_SO(scheme_minus_inf_object);
-  REGISTER_SO(scheme_nan_object);
-#ifdef MZ_USE_SINGLE_FLOATS
-  REGISTER_SO(scheme_single_inf_object);
-  REGISTER_SO(scheme_single_minus_inf_object);
-  REGISTER_SO(scheme_single_nan_object);
-#endif
-    
-  START_XFORM_SKIP;
+void scheme_configure_floating_point(void)
+  XFORM_SKIP_PROC
+/* can be called in any thread */
+{    
 #ifndef DONT_IGNORE_FPE_SIGNAL
   MZ_SIGSET(SIGFPE, SIG_IGN);
 #endif
@@ -270,7 +249,35 @@ scheme_init_number (Scheme_Env *env)
 #ifdef ASM_DBLPREC_CONTROL_87
   to_double_prec();
 #endif
-  END_XFORM_SKIP;
+}
+
+
+void
+scheme_init_number (Scheme_Env *env)
+{
+  Scheme_Object *p;
+
+  REGISTER_SO(scheme_pi);
+  REGISTER_SO(scheme_half_pi);
+  REGISTER_SO(scheme_zerod);
+  REGISTER_SO(scheme_nzerod);
+#ifdef MZ_USE_SINGLE_FLOATS
+  REGISTER_SO(scheme_single_pi);
+  REGISTER_SO(scheme_zerof);
+  REGISTER_SO(scheme_nzerof);
+#endif
+  REGISTER_SO(scheme_plus_i);
+  REGISTER_SO(scheme_minus_i);
+  REGISTER_SO(scheme_inf_object);
+  REGISTER_SO(scheme_minus_inf_object);
+  REGISTER_SO(scheme_nan_object);
+#ifdef MZ_USE_SINGLE_FLOATS
+  REGISTER_SO(scheme_single_inf_object);
+  REGISTER_SO(scheme_single_minus_inf_object);
+  REGISTER_SO(scheme_single_nan_object);
+#endif
+
+  scheme_configure_floating_point();
 
 #if defined(HUGE_VAL) && !defined(USE_DIVIDE_MAKE_INFINITY)
   scheme_infinity_val = HUGE_VAL;
diff --git a/src/racket/src/schpriv.h b/src/racket/src/schpriv.h
index 2ef8bfb090..1aa4183832 100644
--- a/src/racket/src/schpriv.h
+++ b/src/racket/src/schpriv.h
@@ -1773,6 +1773,8 @@ intptr_t scheme_get_semaphore_init(const char *who, int n, Scheme_Object **p);
 # define scheme_exact_one scheme_make_integer(1)
 #endif
 
+void scheme_configure_floating_point(void);
+
 /****** Bignums *******/
 
 #ifdef USE_LONG_LONG_FOR_BIGDIG