diff --git a/ChangeLog b/ChangeLog
index ad5015dd31..746275271f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Nov 28 23:39:01 2012  Koichi Sasada  <ko1@atdot.net>
+
+	* thread.c (rb_mutex_sleep): fix to allow spurious wakeup.
+
+	* NEWS: write about spurious wakeup.
+
 Wed Nov 28 23:37:14 2012  Masaya Tarui  <tarui@ruby-lang.org>
 
 	* NEWS (Thread) remove incompatible changes.
diff --git a/NEWS b/NEWS
index bca93c1b22..62ad75aae4 100644
--- a/NEWS
+++ b/NEWS
@@ -116,6 +116,7 @@ with all sufficient information, see the ChangeLog file.
       * Mutex#lock, Mutex#unlock, Mutex#try_lock, Mutex#synchronize
         and Mutex#sleep are no longer allowed to be used from trap handler
         and raise a ThreadError in such case.
+      * Mutex#sleep may spurious wakeup. Check after wakeup.
 
   * NilClass
     * added method:
diff --git a/thread.c b/thread.c
index 371607b1fa..0b3d009f0a 100644
--- a/thread.c
+++ b/thread.c
@@ -4294,15 +4294,15 @@ rb_mutex_abandon_all(rb_mutex_t *mutexes)
 static VALUE
 rb_mutex_sleep_forever(VALUE time)
 {
-    rb_thread_sleep_deadly();
+    sleep_forever(GET_THREAD(), 1, 0); /* permit spurious check */
     return Qnil;
 }
 
 static VALUE
 rb_mutex_wait_for(VALUE time)
 {
-    const struct timeval *t = (struct timeval *)time;
-    rb_thread_wait_for(*t);
+    struct timeval *t = (struct timeval *)time;
+    sleep_timeval(GET_THREAD(), *t, 0); /* permit spurious check */
     return Qnil;
 }
 
@@ -4334,6 +4334,9 @@ rb_mutex_sleep(VALUE self, VALUE timeout)
  * Releases the lock and sleeps +timeout+ seconds if it is given and
  * non-nil or forever.  Raises +ThreadError+ if +mutex+ wasn't locked by
  * the current thread.
+ *
+ * Note that this method can wakeup without explicit Thread#wakeup call.
+ * For example, receiving signal and so on.
  */
 static VALUE
 mutex_sleep(int argc, VALUE *argv, VALUE self)