diff --git a/ChangeLog b/ChangeLog
index b1fe148655..c4f896c53f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jul  4 22:24:46 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread_pthread.c (get_stack): For NetBSD/FreeBSD, use
+	  pthread_attr_getstack() if possible. and, remove an assumption
+	  of stack growing direction.
+
 Mon Jul  4 20:42:31 2011  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* ext/coverage/coverage.c: revert r32071.  The commit caused SEGV on
diff --git a/thread_pthread.c b/thread_pthread.c
index abb547defb..41d6399c3c 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -479,9 +479,14 @@ get_stack(void **addr, size_t *size)
 # elif defined HAVE_PTHREAD_ATTR_GET_NP /* FreeBSD, DragonFly BSD, NetBSD */
     CHECK_ERR(pthread_attr_init(&attr));
     CHECK_ERR(pthread_attr_get_np(pthread_self(), &attr));
+#   ifdef HAVE_PTHREAD_ATTR_GETSTACK
+    CHECK_ERR(pthread_attr_getstack(&attr, addr, size));
+    STACK_DIR_UPPER((void)0, (void)(*addr = (char *)*addr + *size));
+#   else
     CHECK_ERR(pthread_attr_getstackaddr(&attr, addr));
     CHECK_ERR(pthread_attr_getstacksize(&attr, size));
-    *addr = (char *)*addr + *size;
+    STACK_DIR_UPPER((void)0, (void)(*addr = (char *)*addr + *size));
+#   endif
 # else /* MacOS X */
     pthread_t th = pthread_self();
     *addr = pthread_get_stackaddr_np(th);