diff --git a/ChangeLog b/ChangeLog
index eda21bc269..626f3ec1d9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Feb  6 20:37:42 2009  Tanaka Akira  <akr@fsij.org>
+
+	* signal.c (register_sigaltstack): ignore sigaltstack error.
+	  It fails on OpenBSD 4.4 when pthread library is linked.
+
 Fri Feb  6 18:18:07 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* win32/win32.c (rb_w32_readdir_with_enc): fallback to OS's conversion
diff --git a/signal.c b/signal.c
index 0348f0c995..b952b4e9bb 100644
--- a/signal.c
+++ b/signal.c
@@ -444,8 +444,7 @@ register_sigaltstack(void)
     newSS.ss_size = ALT_STACK_SIZE;
     newSS.ss_flags = 0;
 
-    if (sigaltstack(&newSS, &oldSS) < 0) 
-	rb_bug("register_sigaltstack. error\n");
+    sigaltstack(&newSS, &oldSS); /* ignore error. */
 }
 #endif