diff --git a/ChangeLog b/ChangeLog
index 0f665dbc3a..2c9594642f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Dec  1 15:48:47 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* signal.c (register_sigaltstack): no need to define on non-sigaltstack
+	  platform.
+
 Mon Dec  1 12:00:45 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* cont.c (rb_fiber_start): calls with exact argument number.
diff --git a/signal.c b/signal.c
index 1dfff89b46..cb2fcb3557 100644
--- a/signal.c
+++ b/signal.c
@@ -446,8 +446,6 @@ register_sigaltstack(void)
     if (sigaltstack(&newSS, &oldSS) < 0) 
 	rb_bug("register_sigaltstack. error\n");
 }
-#else
-#define register_sigaltstack() ((void)0)
 #endif
 
 static sighandler_t
@@ -716,7 +714,9 @@ default_handler(int sig)
 #ifdef SIGSEGV
       case SIGSEGV:
         func = (sighandler_t)sigsegv;
+# ifdef USE_SIGALTSTACK
         register_sigaltstack();
+# endif
         break;
 #endif
 #ifdef SIGPIPE
@@ -1124,7 +1124,9 @@ Init_signal(void)
     install_sighandler(SIGBUS, sigbus);
 #endif
 #ifdef SIGSEGV
+# ifdef USE_SIGALTSTACK
     register_sigaltstack();
+# endif
     install_sighandler(SIGSEGV, (sighandler_t)sigsegv);
 #endif
     }