diff --git a/ChangeLog b/ChangeLog
index 27e771e9e1..dae78d955a 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 12:03:47 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ruby.c (process_options): -K and -E in shebang should be reflect to
diff --git a/signal.c b/signal.c
index 317537cae5..0845a3df49 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