diff --git a/ChangeLog b/ChangeLog
index ab021af610..45ce41d805 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Mar  6 21:00:23 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread_pthread.c (USE_SLEEPY_TIMER_THREAD): use more accurate
+	  ifdef condtions.
+
 Sun Mar  3 02:30:36 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* thread_pthread.c (set_nonblock): new helper function for set
diff --git a/thread_pthread.c b/thread_pthread.c
index c67718a362..1faf2755a7 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -53,12 +53,12 @@ static pthread_t timer_thread_id;
 #define USE_MONOTONIC_COND 0
 #endif
 
-#ifdef __native_client__
-/* Doesn't have select(1). */
-# define USE_SLEEPY_TIMER_THREAD 0
-#else
+#if defined(HAVE_FCNTL) && defined(F_GETFL) && defined(F_SETFL) && defined(O_NONBLOCK) && !defined(__native_client__)
 /* The timer thread sleeps while only one Ruby thread is running. */
 # define USE_SLEEPY_TIMER_THREAD 1
+#else
+/* Doesn't have select(1). */
+# define USE_SLEEPY_TIMER_THREAD 0
 #endif
 
 static void