diff --git a/ChangeLog b/ChangeLog
index 97a1832b85..c077dbb557 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Wed Jun 17 12:37:37 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* thread.c (ruby_thread_stack_overflow): call rb_exc_raise() on
+	  stack overflows in the signal handler, if sigaltstack is
+	  available.  On stack overflow (and with sigaltstack), the signal
+	  handler is more likely to have room to create an exception
+	  object.  [ruby-core:23813]
+
 Wed Jun 17 08:14:01 2009  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* complex.c (nucomp_coerce): accepts Complex instances.
diff --git a/thread.c b/thread.c
index fce974acf4..91b957681d 100644
--- a/thread.c
+++ b/thread.c
@@ -1302,12 +1302,21 @@ rb_thread_signal_exit(void *thptr)
     rb_thread_raise(2, argv, th->vm->main_thread);
 }
 
+#if defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK)
+#define USE_SIGALTSTACK
+#endif
+
 void
 ruby_thread_stack_overflow(rb_thread_t *th)
 {
-    th->errinfo = sysstack_error;
     th->raised_flag = 0;
+#ifdef USE_SIGALTSTACK
+    th->raised_flag = 0;
+    rb_exc_raise(sysstack_error);
+#else
+    th->errinfo = sysstack_error;
     TH_JUMP_TAG(th, TAG_RAISE);
+#endif
 }
 
 int
diff --git a/version.h b/version.h
index 05177b29ac..4c82915df3 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "1.9.1"
 #define RUBY_RELEASE_DATE "2009-05-22"
-#define RUBY_PATCHLEVEL 184
+#define RUBY_PATCHLEVEL 185
 #define RUBY_VERSION_MAJOR 1
 #define RUBY_VERSION_MINOR 9
 #define RUBY_VERSION_TEENY 1