diff --git a/ChangeLog b/ChangeLog
index 0f513e3902..6bc4917129 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Thu Jul  1 16:26:42 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* thread_pthread.c (thread_start_func_1): don't call
+	  native_thread_init_stack(th) on cygwin to avoid the segv
+	  introduced by r27789. Cygwin's signal implementation is half
+	  baked so USE_SIGNALSTACK is not defined and it needs another
+	  treatment.
+
 Thu Jul  1 13:00:54 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* common.mk (test-knownbug): ignore known bugs.
diff --git a/thread_pthread.c b/thread_pthread.c
index 2136874bd3..95fb77a7f8 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -364,7 +364,9 @@ thread_start_func_1(void *th_ptr)
 	rb_thread_t *th = th_ptr;
 	VALUE stack_start;
 
+#ifndef __CYGWIN__
 	native_thread_init_stack(th);
+#endif
 	/* run */
 	thread_start_func_2(th, &stack_start, rb_ia64_bsp());
     }